Videos crashing X

[Craig Puchta]

I'm wondering if anyone else is having this issue or how I go about
finding out what is causing this.

There seems to be no rhyme or reason to when this happens but I'll
start up a video, regardless of player or video and X crashes and
drops me back to GDM login screen. Sometimes though, it freezes X and
I can hear sound but nothing on X works, Ctrl +Alt+Backspace won't
even work when this happens.
This can happen 5mins after logging in or 10 hours after logging in.
I just don't even know where to start looking, logs? But what ones?
Any ideas?