Sound doesn't work everywhere.

I installed MSN Messenger 5.0 and everything worked great. Until the next day. Then the MSN sound doesn't work, and Warcraft 3 doesn't have sound, but Adium, firefox, iTunes, and the system seem to work fine. Any ideas what would cause the sound to quit working in some applications?

Never mind. Found my old post and didn't think it was the same, but it is. I just opened grage band then closed it