Personally I've had the GSOD occur during light GPU use, such as Rocketdock's animations or iTunes' CoverFlow. What I tried was disabling my GPU-related startup applications one by one, until I found out what the culprit was. And well, turns out it was CCC (Cat 9.12 Hotfix).
Prior to this, I had hand-modified a CCC profile with higher 2D clocks and voltages, as I had been getting the GSOD randomly and heard about this being a fix. And for a while, it most certainly did work. That is of course, until I started getting the GSOD a few seconds after any measure of GPU usage.
Since disabling CCC from startup, I haven't seen the GSOD at all. Whether I'm doing some heavy gaming, or simply browsing through my CoverFlow playlist, it runs as it should. Though I do have a nagging hunch that disabling my CCC profile will cure this problem of mine.
In any case, I only stated this since in the OP's first post, he mentioned faulty RAM modules being a likely cause of GSOD occurrences during light GPU usage. Not saying that may not be the case, but my situation also presents another possibility that may not require an RMA after all.