Originally Posted by Maylander
This error can be cause by quite a few different issues actually. In my case it was a simple matter of the GPU being a bit too strong for the games I was playing, so it ended up going into idle mode and Win 7 decided it would be a brilliant move to swap to the integrated Intel GPU. I hate those things, they've caused so much trouble for me. If only there was a way for Windows to never even take the damn thing into consideration.
Anyway, the solution for me was to manually increase the idle GPU speed so it was always considered active. The idle speed is usually set to 157/300, and I think I pretty much doubled that. However, it's a simple matter of experimenting - you want it set high enough to never get the error, but not so high it'll grow hot or become too loud.