Question: When I try to get the identifier of an EKEvent, all I get is a nil value. Since in iOS5 EKEvent is a subclass of EKCalendarItem, I figured I might be able to get the EKCalendarItem's UUID, but that returns nil as well. 

Every now and then I also get this error while trying to access the identifier or UUID property: 

```
CADObjectGetInlineStringProperty failed fetching uniqueID for EKPersistentEvent with error Error Domain=NSMachErrorDomain Code=268435459 "The operation couldn’t be completed. (Mach error 268435459 - (ipc/send) invalid destination port)"

```

I've been stuck on this problem for quite some time now, but figured it would be iOS5 beta related. But since we're now at iOS5, it's still not working.

Answer: 
In my app I found out that if you ask for the eventIdentifier when the eventStore that fetched it has been released, it returns nil. But if you ask for the eventIdentifier before it will return the id ok. You can then release the EKEventStore instance and ask for the identifier with no problem.... Seems that it needs the eventStore to retrieve the id, but I get no warnings.
For me, the `eventIdentifier` is null because I was not setting the `endDate`. So generally the `eventIdentifier` can be null if there are any error on creating that event. You can check for errors like this:

```
NSError *err = nil;
[store saveEvent:event span:EKSpanThisEvent commit:YES error:&err];
NSLog(@"Error : %@",err);

```