blue screen no text?

Hey, i was using my computer the other day and I got a blue screen, but no text or anything. It was just plain blue, and I had to power off to restart. Then my windows firewall comes up asking me whether or not i want to unblock xwin.

I was just typing stuff into a ssh client. Any ideas? Computer is pretty new (3 months, laptop, xp sp2, 1.5 gig ram, 2ghz processor)

Cheers,

Bluemouse