Bug#660734: firmware-linux-nonfree: Debian Desktop Installation unusable because radeon firmware is missing
> After a fresh debian installation on my laptop, all the screen goes black and grey after a restart, because the radeon-firmware is missing. This also happens in recovery mode.
> I had to manually fix this by copiing the firmware files after starting from a debian CD ROM. I first tried to fix it with different kernel boot parameters, but they all did not help.
> The problem does not occure when installing debian squeeze, neither when doing an upgrade from squeeze to wheezy.
> This propably concerns other Laptops/Computers with ATI grapic cards. Maybe it is related to GNOME 3 which needs 3D support? (just a guess)
> At least, a hint in the installer would be nice so that a user knows he has to use unfree firmware or else he will be unable to use the system.
As a simpler workaround you could try passing radeon.modeset=0 to
grub's boot options. Once booted you could then install the firmware
to resolve it.
Still this is an annoying problem if you are just trying to run up a new system.