Oh, okay, I think I know what you guys are talking about. If so, then I think it is just a rendering thing, and will vary from computer to computer, as that's how it's worked for me when I've (infrequently) seen it. I think my old laptop did this fairly often, in fact, but I haven't played Descent on it in quite awhile.
Actually, the real question was, "who paid for the old laptop?" .