Should i worry about sandboxd deny file-write-data'
I have a database app. Single entity. I've just upgraded it to enable iCloud sync. Here's my PSC in my app delegate:

    - (NSPersistentStoreCoordinator *)persistentStoreCoordinator
    {
    if (persistentStoreCoordinator__ != nil)
    {
        return persistentStoreCoordinator__;
    }
    NSString *storePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"Logbook.sqlite"];
    NSURL *storeURL = [NSURL fileURLWithPath:storePath];
    
    persistentStoreCoordinator__ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    
    
    NSPersistentStoreCoordinator* psc = persistentStoreCoordinator__;
    
    if (IOS_VERSION_GREATER_THAN_OR_EQUAL_TO(@"5.0")) {
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            NSFileManager *fileManager = [NSFileManager defaultManager];
            NSLog(@"We're iniOS 5!");   
            // Migrate datamodel
            NSDictionary *options = nil;
            
            // this needs to match the entitlements and provisioning profile
            NSURL *cloudURL = [fileManager URLForUbiquityContainerIdentifier:@"XXXXXXXXXX.com.burgul.Logbook"];
            NSString* coreDataCloudContent = [[cloudURL path] stringByAppendingPathComponent:@"data"];
            if ([coreDataCloudContent length] != 0) {
                // iCloud is available
                NSLog(@"...and  iCloud is live!");
                cloudURL = [NSURL fileURLWithPath:coreDataCloudContent];
                
                options = [NSDictionary dictionaryWithObjectsAndKeys:
                           [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                           [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                           @"Logbook.store", NSPersistentStoreUbiquitousContentNameKey,
                           cloudURL, NSPersistentStoreUbiquitousContentURLKey,
                           nil];
            } else {
                // iCloud is not available
                 NSLog(@"...but  iCloud unavailable!");
                options = [NSDictionary dictionaryWithObjectsAndKeys:
                           [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                           [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                           nil];
            }
            
            NSError *error = nil;
            [psc lock];
            if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error])
            {
                NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
                abort();
            }
            [psc unlock];
            
            dispatch_async(dispatch_get_main_queue(), ^{
                NSLog(@"asynchronously added persistent store!");
                [[NSNotificationCenter defaultCenter] postNotificationName:@"RefetchAllDatabaseData" object:self userInfo:nil];
            });
            
        });
        
    } else {
        NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                                 [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                                 nil];
        
        NSError *error = nil;
        if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error])
        {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
    return persistentStoreCoordinator__;
    }

I consistently get this error but iCloud sync appears to work between iPhone and iPad. Should I worry? Why does it occur?:

    Feb 28 22:23:40 unknown Logbook[2191] <Warning>: We're iniOS 5!
    Feb 28 22:23:41 unknown Logbook[2191] <Warning>: Root view loading...
    Feb 28 22:23:41 unknown Logbook[2191] <Warning>: ...and  iCloud is live!
    Feb 28 22:23:41 unknown sandboxd[2192] <Notice>: Logbook(2191) deny file-write-data             /private/var/mobile/Library/Mobile Documents/XXXXXXXXXX~com~burgul~Logbook
    Feb 28 22:23:42 unknown Logbook[2191] <Warning>: -[PFUbiquityTransactionLog loadComparisonMetadataWithError:](220): CoreData: Ubiquity:  Error encountered while trying to load the comparison metadata for transaction log: <PFUbiquityTransactionLog: 0x1fc020>
		transactionLogLocation: <PFUbiquityLocation: 0x1fb3a0>: /private/var/mobile/Library/Mobile Documents/XXXXXXXXXX~com~burgul~Logbook/data/mobile.7B7D20A-AD93-5631-9E0D-61B5E5AE1DB0/Logbook.store/1DGRB5~3_aHWVwlP9v9teBUHYhFYHcmj6kWm8HjF~8=/5837F007-B39E-42C2-A3D1-F69998C2F251.1.cdt
		transactionNumber: (null)
	
    Error: Error Domain=NSCocoaErrorDomain Code=134301 "The operation couldn’t be completed. (Cocoa error 134301.)" UserInfo=0x172880 {reason=Error during property list parsing during import or opening of log file at location: <PFUbiquityLocation: 0x1fb7d0>: /private/var/mobile/Library/Mobile Documents/WSL474W2X9~com~burgul~Logbook/data/mobile.7B7DC20A-AD93-5631-9E0D-61B5E5AE1DB0/tempLogs.nosync/Logbook.store/1DGRB5~3_aHWVwlP9vteBUHYhFYUHcmj6kWm8HjF~8=/5837F007-B39E-42C2-A3D1-F6998C2F251.1.cdt, error: Error Domain=NSCocoaErrorDomain Code=134301 "The operation couldn’t be completed. (Cocoa error 134301.)" UserInfo=0x185e80 {missingFile=/private/var/mobile/Library/Mobile Documents/WSL474W2X9~com~burgul~Logbook/data/mobile.7B7DC20A-AD93-5631-9E0D-61B5E5AE1DB0/tempLogs.nosync/Logbook.store/1DGRB5~3_aHWVwlP9v9teBUHYhFYUHmj6kWm8HjF~8=/5837F007-B39E-42C2-A3D1-F69998C2F251.1.cdt}}
    Feb 28 22:23:42 unknown Logbook[2191] <Warning>: -[PFUbiquityTransactionLog loadComparisonMetadataWithError:](220): CoreData: Ubiquity:  Error encountered while trying to load the comparison metadata for transaction log: <PFUbiquityTransactionLog: 0x171780>
Should i worry about sandboxd deny file-write-data'
===

I have a database app. Single entity. I've just upgraded it to enable iCloud sync. Here's my PSC in my app delegate:

    - (NSPersistentStoreCoordinator *)persistentStoreCoordinator
    {
    if (persistentStoreCoordinator__ != nil)
    {
        return persistentStoreCoordinator__;
    }
    NSString *storePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"Logbook.sqlite"];
    NSURL *storeURL = [NSURL fileURLWithPath:storePath];
    
    persistentStoreCoordinator__ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    
    
    NSPersistentStoreCoordinator* psc = persistentStoreCoordinator__;
    
    if (IOS_VERSION_GREATER_THAN_OR_EQUAL_TO(@"5.0")) {
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            NSFileManager *fileManager = [NSFileManager defaultManager];
            NSLog(@"We're iniOS 5!");   
            // Migrate datamodel
            NSDictionary *options = nil;
            
            // this needs to match the entitlements and provisioning profile
            NSURL *cloudURL = [fileManager URLForUbiquityContainerIdentifier:@"XXXXXXXXXX.com.burgul.Logbook"];
            NSString* coreDataCloudContent = [[cloudURL path] stringByAppendingPathComponent:@"data"];
            if ([coreDataCloudContent length] != 0) {
                // iCloud is available
                NSLog(@"...and  iCloud is live!");
                cloudURL = [NSURL fileURLWithPath:coreDataCloudContent];
                
                options = [NSDictionary dictionaryWithObjectsAndKeys:
                           [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                           [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                           @"Logbook.store", NSPersistentStoreUbiquitousContentNameKey,
                           cloudURL, NSPersistentStoreUbiquitousContentURLKey,
                           nil];
            } else {
                // iCloud is not available
                 NSLog(@"...but  iCloud unavailable!");
                options = [NSDictionary dictionaryWithObjectsAndKeys:
                           [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                           [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                           nil];
            }
            
            NSError *error = nil;
            [psc lock];
            if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error])
            {
                NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
                abort();
            }
            [psc unlock];
            
            dispatch_async(dispatch_get_main_queue(), ^{
                NSLog(@"asynchronously added persistent store!");
                [[NSNotificationCenter defaultCenter] postNotificationName:@"RefetchAllDatabaseData" object:self userInfo:nil];
            });
            
        });
        
    } else {
        NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                                 [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption,
                                 nil];
        
        NSError *error = nil;
        if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error])
        {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
    return persistentStoreCoordinator__;
    }

I consistently get this error but iCloud sync appears to work between iPhone and iPad. Should I worry? Why does it occur?:

    Feb 28 22:23:40 unknown Logbook[2191] <Warning>: We're iniOS 5!
    Feb 28 22:23:41 unknown Logbook[2191] <Warning>: Root view loading...
    Feb 28 22:23:41 unknown Logbook[2191] <Warning>: ...and  iCloud is live!
    Feb 28 22:23:41 unknown sandboxd[2192] <Notice>: Logbook(2191) deny file-write-data             /private/var/mobile/Library/Mobile Documents/XXXXXXXXXX~com~burgul~Logbook
    Feb 28 22:23:42 unknown Logbook[2191] <Warning>: -[PFUbiquityTransactionLog loadComparisonMetadataWithError:](220): CoreData: Ubiquity:  Error encountered while trying to load the comparison metadata for transaction log: <PFUbiquityTransactionLog: 0x1fc020>
		transactionLogLocation: <PFUbiquityLocation: 0x1fb3a0>: /private/var/mobile/Library/Mobile Documents/XXXXXXXXXX~com~burgul~Logbook/data/mobile.7B7D20A-AD93-5631-9E0D-61B5E5AE1DB0/Logbook.store/1DGRB5~3_aHWVwlP9v9teBUHYhFYHcmj6kWm8HjF~8=/5837F007-B39E-42C2-A3D1-F69998C2F251.1.cdt
		transactionNumber: (null)
	
    Error: Error Domain=NSCocoaErrorDomain Code=134301 "The operation couldn’t be completed. (Cocoa error 134301.)" UserInfo=0x172880 {reason=Error during property list parsing during import or opening of log file at location: <PFUbiquityLocation: 0x1fb7d0>: /private/var/mobile/Library/Mobile Documents/WSL474W2X9~com~burgul~Logbook/data/mobile.7B7DC20A-AD93-5631-9E0D-61B5E5AE1DB0/tempLogs.nosync/Logbook.store/1DGRB5~3_aHWVwlP9vteBUHYhFYUHcmj6kWm8HjF~8=/5837F007-B39E-42C2-A3D1-F6998C2F251.1.cdt, error: Error Domain=NSCocoaErrorDomain Code=134301 "The operation couldn’t be completed. (Cocoa error 134301.)" UserInfo=0x185e80 {missingFile=/private/var/mobile/Library/Mobile Documents/WSL474W2X9~com~burgul~Logbook/data/mobile.7B7DC20A-AD93-5631-9E0D-61B5E5AE1DB0/tempLogs.nosync/Logbook.store/1DGRB5~3_aHWVwlP9v9teBUHYhFYUHmj6kWm8HjF~8=/5837F007-B39E-42C2-A3D1-F69998C2F251.1.cdt}}
    Feb 28 22:23:42 unknown Logbook[2191] <Warning>: -[PFUbiquityTransactionLog loadComparisonMetadataWithError:](220): CoreData: Ubiquity:  Error encountered while trying to load the comparison metadata for transaction log: <PFUbiquityTransactionLog: 0x171780>