Fedora 17 boot problem

[Arkadiusz Kotarba]

Hi.
After installation everything I see is the top edge of the screen, rest 
is just black. No matter if I install from livecd/dvd or try upgrading 
from Fedora 16 through dvd installer. Same if I try to boot with 3 
instead of rhgb and quiet options (runlevel 3 if I remember correctly).
Fedora 16 was running fine, without any problems.

Hardware: Phenom II X6 1090T, AMD HD 6870, 8GB RAM, HDD WD 1TB

Any ideas?
Thanks in advice.
Athane