stivhatten The one error in your dxdiag could be nothing meaningful at all, or it could be something, but the nature of the error doesn't make that clear on its own. So there's no reason to worry based on that info alone, and currently no other concerning info of that nature. The fact that the screen goes black while you're playing is probably more significant.
I doubt that setting the fps limit to 30 would cause the black screen, but the important question is whether it happens again. And you can set a limit of 60 or 59 or whatever works for you.
