Please read here (in this destroyed thread, where people are ranting about the premium membership):

I played Warsow and suddenly the monitor went black. After a reboot it stayed black and if I use an external monitor, I can see the normal BIOS screen, but with small green lines all over the place. I get to GRUB (which is screwed up and shows some weird symbols for several characters), kernel is loaded and when kms is enabled the screen goes black again.
It's an AMD 6970M and worked fine for a couple of months after I installed it. So I ask the experts if those are symptoms of a fried card...
What makes me wonder is why the characters in GRUB are not properly displayed regardless of the green lines.