Can't save files in some applications I some application, such as Xcode, Pages and Pixelmator 2, when I save, I get an error about not having the permissions to save the file:

"The document “[document name]” could not be saved. You don’t have permission. To view or change permissions, select the item in the Finder and choose File > Get Info."

There's nothing wrong with the permissions. I can edit and save the same files from other applications, such as Textmate, Text Edit and Preview, without problems. I can also create a new project in Xcode, and it generates all the files without problem, but I still get the error message when trying to save any changes in these.

I'm running Lion, clean installed.

Edit: here's an example ls -l on some files I can't edit:

-rw-r--r--  1 ulrikdamm  staff  4221 Nov  1 08:36 french.strings
-rw-r--r--  1 ulrikdamm  staff  3755 Nov  1 10:53 german.strings
-rwxrwxrwx  1 ulrikdamm  staff  4147 Oct 31 23:49 hungarian.strings


even with full permissions, I can't save them. And it's not only some files that cannot be saved, it's all files, no matter what their permission level is.

Edit 2: folder permissions:

drwx------+ 32 ulrikdamm  staff  1088 Nov  4 14:00 Desktop


(yes, it's on my desktop)

id output:

uid=501(ulrikdamm) gid=20(staff) groups=20(staff),402(com.apple.sharepoint.group.1),401(com.apple.access_screensharing),12(everyone),33(_appstore),61(localaccounts),79(_appserverusr),80(admin),81(_appserveradm),98(_lpadmin),100(_lpoperator),204(_developer)


Edit 3: I tried making a new user, and saving files there works without problems. Can it has something to do with some user settings being messed up?
Since you haven't used ls -le as recommended, we don't know what the access control list looks like, but there might be something going on there that is preventing you from being able to write the files. The fact that a newly created user CAN edit the files makes me even more suspicious.

This command will remove ALL access control list entries from the folder and all its subfolders and files:

sudo chmod -RN path/to/folder/containing/files


Once you've cleared the access control list, try resetting the ownership like so:

sudo chown -R ulrikdamn:staff path/to/folder/containing/files


Now grant permissions like so:

sudo chmod -R u+rwX,g+rX,o+rX path/to/folder/containing/files


This gives you full read/write permissions. The "staff" group and all other users get full read permissions. Using an uppercase X, sets the execute bit for all directories within the tree, but leaves the execute bit for regular files as is. 

Lowercase x would set the execute bit for all folders AND files. The execute bit must be set for a directory in order to read its contents. If you'd like to give write permissions to the group or others, switch out for g+rwX or o+rwX as necessary in the last command.

Here I'm passing in a folder path. If you want to pass in a single file, just remove the -R from each command. The R makes the command recursive, applying it to an entire directory tree. Without it, the command will modify the permissions for a single file or folder passed in.