OK. Thanks for running the test and posting back. Well, that pretty much leaves us with the GPU. The GPU is integrated within the logic board which means that the entire board will have to be changed - if that's the problem.

Normally I would suggest running the Apple Hardware Test, but since the AHT is not that reliable and your problem seems to point to the GPU, I don't see much use in doing it. However, if you would like to give it a try, follow these directions from Apple: Link

If your machine is still under warranty or Apple care, make an appointment with the genius bar and take it on in. If it's not under warranty, you probably have a decision to make about repairing it.

Regards.