I can play AVI, WMV, etc. in VLC, mplayer, etc. (Ubuntu Linux 8.04). However, mpeg doesn't play, it hangs and crashes X, forcing a hard reboot. Does anyone have a suggestion or solution?

Try using a different sound daemon, I had some problems using ESD and changed to ALSA...problem solved.

I use ALSA, not ESD. It's always running with pulseaudio, however.

EDIT: I also failed to mention that the sound plays on the videos, the video doesn't play and the mouse can still move. I just can't X-out or click anything else -- the keyboard doesn't work, so Ctrl+Alt+Bksp is a pointless endeavor.