Well, turning the Steam overlay off fixes the problem…. Only now I can't take Steam screenshots. Okay so, this is weird. I did what you said, then reactivated Steam overlay for the game, then ran it from the Steam browser, and the problem disappeared! I'm now able to use the Steam overlay, and the VAB and SPH are both accessible again! But the weird part is that, as you can see from that screenshot, it claims that I didn't actually install anything. It seems to be saying that I already had everything installed that I tried to install. But if that's the case, then why would the bug have gone away? It happened consistently every time I tried to start a new game, before. And yet now it's gone, despite that it would seem as though I haven't done anything. I wish I would have checked, before deactivating the Steam overlay, and after reactivating it but before attempting to install that driver, whether I was still getting the graphical bug in the VAB/SPH. Then I might have known for sure what fixed it, or if it truly did just fix itself on its own (as it seems to have). Ah well. Thanks for your help! The problem is resolved.