At the moment I'm having big issues with both 12.10 and the 12.11 Beta. I haven't worked out the issue is, as it starts as soon as I reboot after installing either of these drivers
(on either Windows 8 release preview, or Windows 7 Ultimate x64).
I'm running two Radeon HD 6970's in Crossfire, with 2 monitors each running at 2560x1440.
As soon as I roll back to my old drivers, it's fine again.