>thanks for your reply. I do actually have a pc temperature monitor
>programme. if it was that was the problem then the pc would restart
>whenever.
Not really. You’d experience it much more often with programs that stress your cpu, like Cinema for instance–particularly during rendering.
>I only have this problem with cinema.
Well, it’s probably not cooling then.
The next best guess is OpenGL drivers. Try disabling OGL in preferences and see if that eliminates the problem.