From time to time my macbook will have this strange malfunction. It usually seems to happen after I've been using vlc for a while. For example, I just finished watching a movie, and none of my applications will launch. The ones that are already open work fine. So I logout and try to log back in. But then it just gives me the progress bar and reverts back to the login screen, so I can't login. The only thing that fixes this is restarting my computer. Now, this doesn't happen every time after I close vlc, but thats when I've noticed it most.

I'm running 10.6.4 on my macbook 4.1, intel core 2 duo 2.4GHz

Any ideas?