Well, the 14.70 drivers still seem to have this problem, but to a lesser extent. Whereas before when I ran the DOS prompt full-screen my computer would crash, now the prompt just looks messed up. I can alt-tab out of it and continue to use the computer. So at least this is a step in the right direction. I'll try even earlier ones and see if it is any better.
Also, I get random green flashes on the windows logo screen. I only get those with the nvidia drivers - when using the 'standard vga adapter' option, it doesn't do that.
Hmmm... with 12.42, I can actually see the maximized DOS prompt. However, when I try to leave it, the whole screen goes green. Also, the flashing during the windows logo at startup has been becoming less and less the further back I go. I'll try another version...
...11.00 doesn't do it either. Also, it lists it as MX instead of MX/MX400, which I'm sure is what it was listed as when it worked. So I've stopped going back and put 21.83 back on. At least windows starts under it. But what could be causing this dos issue? I know it must be related to the drivers in some way because every time I switched driver versions, the problem changed nature somewhat.