My cards are clocked at 157/300 in 2D mode.
850/1200 in 3D mode. I havent noticed any flickering as you say.
A lot of people have issues with different drivers for these cards. Read the AMD game forums.
I'm having huge success with the 11.4a hotfix drivers. These are preview drivers.
Try some different drivers.Maybe this will help.
Since you just got this card,have you checked if your PSU has enough power to run it?
This has been the cause of many problems.
Good luck.These cards are very good.