Why is Keychain behaving erratically?
Sounds like this was due to them creating a new user (502) and naming it the same as the old user, and copying all your old files in.  The problem is that the new user account ID doesn't match the old user ID.  What needed to be done was a chown -R 502 on your whole user directory.  Too bad you started afresh.  Sidenote: Trying to restore in this fashion almost never works well.  Wipe the disk, re-install a good OS, and then restore from a TM or other backup if available.  I've never had a problem using that method, but I've definitely had problems using the method you describe.  Better luck next time.