Still existing lock-ups with i9100

I have Inspiron 9100 with Mobility Radeon 9700 w 128mb. Since the purchase, I had experienced system lockups when running videocard-stressing processes (games, screensavers, and hardware accelations on 2D applications like Power Point). The omega driver failed to fix the problem and after sending my laptop in twice for the repair did not resolve the issue. Dell Inc. is now blaming the problem on the software but according to my research on the online and from my experience, it is definitely a hardware issue. Did anyone had same problem as I have and was able to get it resolved?