"Login Items" refuse to be removed - Please Help

I have tried searching but apparently there is something prohibiting the normal function of OS X. There are 6 Login Items (Sys Prefs->Users->Login Items) that magically reappear every reboot after deleting them. I first unlock the Pref Pane in the lower right corner, but it makes no difference. The login items happily remove from the list, but always reappear.

The problem began in 10.6, and I hoped an upgrade to Lion would repair what ever is prohibiting the removal. I searched via google and MR, and the best suggestion I found was to delete the "apple.com.dock.plist" and "apple.com.launchservices.plist" under User/Library/Preferences. This unfortunately did not work.

Any suggestions would be welcomed. There is only one user account on this Mac and its an Admin of course.

P.S. this machine is a friend of mines, and it has been used primarily by a young child who is definitely responsible for the problem in the first place.

 

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For the record, repairing permissions and using Onyx to rebuild LaunchServices & shared cache only removed Preview from the list. All other 3rd party apps/services still will not remove