Then, after I'd finally got through that part without it crashing, a new bug happened. The screen went black, like before, but it hadn't crashed. Anything that moved became visible again and if I move the mouse cursor around it cleans away the black. This has happened about 4 times in just a few minutes. Going to the options screen resets it, but it's still really annoying.
I'm playing it on XP, with the unofficial 1.3 installed and the mod that lets you use the mouse wheel and some other things. I guess it might be that last thing causing the problem since it does change some graphical things, but I've had that installed since I started playing a few days ago, with no problem until now.