I have the Win 7 Ati driver preview package, the driver and CCC. I have a HD3450. All is good except every other reboot here and there when it would get to the desktop the DT and the taskbar would be black. I could still see the taskbar but it was blacked out with a little color and I could mouse over the icons and see the popup labels.
After about 30 seconds later from getting to the desktop it would come back but the taskbar would be blank of icons. Well, I disabled the CCC from startup and also set the Ati External Event Utility service to manual.
It stopped this problem for me, so far.