Error trying to backup both iPhone4 and iPad (1) after 4.3/iTunes/XCode updates
I would try manually checking the backups folder(username/Library/Application Support/Mobilesync)and then deleting anything in there. That error message makes me think Xcode but you could try resetting Sync History from preferences in iSync and resetting the SyncServices folder as per http://support.apple.com/kb/ts1627 . Doing that will wipe sync settings for your iPhone so you will have to re-check the information you want to sync in iTunes. I am running Xcode 4 on 10.6.7 and I have not run into this issue. Hopefully this resolves the issue, let me know if this helps. Also as per the last suggestion I would recommend following the instruction on the apple support site for reinstalling iTunes @ http://support.apple.com/kb/ht1224