Originally Posted by Daveecee
Is there anything else that could be causing this?
The Dock preferences could be confused somehow. Try trashing them. You can find them in
yourhomefolder/Library/Preferences/com.apple.dock.plist
After trashing log out and back in and see if the problem persists.
Note that after trashing the Dock preferences file you would have to setup all Dock preferences again including the applications you like to have in the Dock as well as all Exposé settings.