Apple iMac with OS X Lion, graphics are not working. Is that OS problem?

I am having 2011 27" iMac in my core i7 and AMD Radeon HD 6970M 2GB with the outside displays. I think that most of the graphical issues are present in the outside displays but here in my case the menu bar, dock and volume popup all appeared distorted on the main display. I never had these issues with Snow Leopard but as far as I can tell its some kind of graphics driver issue, don't know how this wasn't spotted in the beta. recommend me to resolve this type of the Graphical issues with 2011 iMac and Lion.

In was also having this type of the issue, with my iMac Core i7.4 with the 2GB Graphics Card. For resolving that I have called apple care & informed them. After that I called the apple care & tell them so they escalate this issue. When I called them they sent me a file to Capture the Knowledge of my computer to see what happened & what caused it. in the event you are experiencing this issue write here to tell apple about & call apple care or see the genius bar. & after that I found that this computer ought to be able to connect with 6 screens simultaneously.

After reading the post I came to know that I ma also having the same problem. And in my case it seems to crop up randomly. Today I was reading an news story online and when I went to check my Dashboard, it had it, after checking for that When I returned to my desktop I see that everything was fine. Dashboard had this graphical problem also. Before facing this problem I had the issue on my outside monitor and one time on my primary built-in iMac monitor.

Still I am having the same problem. I have now decided to change the graphic cad or else I will try to downgrade to the previous version of the operating system. Here I want just suggestion that what will be better for me? Please reply me for this.