Kind of late, I know, but I just ran into this same problem reinstalling Homm5 on my new build and I'm wondering if you ever got it sorted out? I've found other postings on the same issue - for example here
- but none of the 'work arounds' work for me. Seems to be the combination of Vista, 4GB of RAM and an 8800GTX - all of which I now have. I believe it is specific
to the GTX model and shouldn't be a problem on the newer GT or GTS but I'm not positive.
I've also found I needed to ditch my wireless mouse for a wired one or it constantly gets 'stuck' or freezes, even on the desktop. Especially sucks in games, some were minor but Homm5 was horrible, so much so it was hard for me just to get the heck out once in. Never mind the 'fine for a second and then bam
washed out' low resolution textures issue. [sigh]
Anyway, perhaps one of the things that worked for other people in the linked post will work for you. Or someone in the same boat.