и аз съм с същата видео карта и видях бая зор докато се справя с проблема, имах същия проблем и бая се рових из гоогле-то и справих се на някъв късмет

мисля че това ще ти помогне следвай инструкцийте:
aptitude update
aptitude install fglrx-control fglrx-driver fglrx-kernel-src module-assistant mesa-utils
* Step 1: Change to kernel and kernel module source code directory.
cd /usr/src
* Step 2: Prepare your system to build new kernel modules.
module-assistant prepare
* Step 3: Build the fglrx kernel module.
module-assistant a-i fglrx
* Step 4: Make a copy of your xorg.conf file:
cp /etc/X11/xorg.conf /etc/X11/xorg.conf.todaysdate
* Step 5: Edit your /etc/X11/xorg.conf file, and set your display driver to fglrx
*
Locate the device section and add the corresponding lines Section "Device".
Section "Device"
Driver "fglrx"
Option "VideoOverlay" "on"
EndSection
* Driver line is probably currently set to "radeon" or "ati". Remember which name you have because you will use it in step #7.
* Also enable XVideo in Extentions
Section "Extensions"
Option "XVideo" "Enable"
EndSection
* Step 5: Exit Gnome (or KDE, just get out of X Windows), press ctrl-alt-F1 to get a console, login as root.
* Step 6: Stop Gnome Display Manager:
/etc/init.d/gdm stop
Or KDE Display Manager
/etc/init.d/kdm stop
Or X Display Manager
/etc/init.d/xdm stop
* Step 7: Remove the old kernel module
modprobe -r radeon
* Step 8: Load the new kernel module
modprobe fglrx
* Step 9: Start the Display manager (substitude gdm with kdm or xdm)
/etc/init.d/gdm start
* Step 10: Test the 3d acceleration
glxinfo | grep direct
* Step 11: Test the xvideo extension
xvinfo