The first thing to do for looking into this is an acklog of the problem.

6.40.5 was an old version from pre-Vista ages, so of course we can't guarantee its Vista compatibility. On the other hand, although this was not 'officially' tested, I know that all old A6 versions run fine under Vista. Even A5 was reported to run under Vista.

So I suspect it's a different problem that also occurs under XP, but does not lead to a crash there for some random reason. Maybe some allocated object is not freed.

You should definitely update to A6.60, at least. We can then also look into the problem when you send us an A6.60 or, much better, an A7 version of your game.