Macbook, Mac OS X (10.6)
i had this exact problem and solved it with a similar method to daeron's. osx seems to be very fussy about ownership and permissions on files. this problem happened with me when i made a new user area to solve SMB problems.
basically, the fix for me was to delete the plist files in preferences as already mentioned, but also to make myself the owner of the applications folder and then clicking the 'apply to enclosed items' link under the little cog when you are on folder info.
hope that helps!
CJBigham your suggestion worked for me. Held down Shift key during startup and logged into Safe Boot. I then went into Login Items and was able to delete everything in the list, then restarted and Login Items behaved normally after that. Thanks!
Dr Raven
That's great, I'm glad you found the tip useful. The same problem might reoccur down the road but at least there is a solution that seems to work & will get the login stuff back on track.
+1 to cjbigham answer, this was the only thing that worked for me. (Hold down shift during startup for Safe Mode, then delete all login items and re-add the ones you want.)
This also cleared up a login issue I had where os x would constantly ask me to log in twice.
Login items disappear after restart
