derSammler wrote:
Judging from the screenshot, it's pretty much the VGA BIOS ROM that is corrupted.
Not if it boots correctly into DOS text mode in the first place.
If the VGA BIOS ROM contents is shadowed and that copy in RAM gets corrupted, possible, but it should corrupt the code in BIOS as well so it would crash pretty quickly when changing video modes.
Maybe caching, ROM shadowing configuration or memory manager configuration issue. I'd disable EMM386 or at least double check its parameters, maybe HIMEM as well. Then which memory areas are shadowed, and if there is a memory mapped peripheral like a network adapter that overlaps the video BIOS area. Also a good test is that If it works in another PC, then the video card should be fine.