In order to use vesafb instead of radeonfb, I added kernel boot parameter
vga=0x301, and this problem was gone.
I also found that Matrox G450 which uses matroxfb shows same problem,
and workarounded with vga=0x301 too.
New udev-071-0.FC4.1 breaks gdm login screen for PC with ATI Radeon.
Many white and black vertical lines displayed whole screen.
When I switch console to 1 and back to 7, login screen is displayed fine.
It seems related to framebuffer console?
I have two Radeon PC, one is laptop which has Radeon Mobility U1,
another box has Radeon 7000/VE AGP card.
Both of them shows same problem.
The kernel-2.6.14-1.1656_FC4 and new udev show this problem too.
Rawhide or FC5T2 do not show this problem.