Hi,
I have not used an ati card for a longer time now.
So anyone may correct me if I'm wrong.
Isn't it nessesary to switch kernelmodesetting off in kernel command line (radeon.modeset=0 in /etc/default/grub) when using fglrx driver?
Best results I had when my 20-fglrx.conf only assinged the driver, nothing else.
Section "Device"
Driver "fglrx"
EndSection
If there is a legacy driver available in fixes I would try this one first. If it's not working then I would try experimental.
And may be you want to install fglrx-legacy-modules-dkms out of the same repo also.
Greets
ayla