I'm using Vista 32 bit, I installed the 1.6.5 update, and I've tried the xp compatibility method, but it had zero effect.
It's also worth noting that for me, this problem got worse and worse the farther into the game I got. When I started out it crashed maybe once in 2-3 hours and only in battle mode (and not because of DEP, it gave some memory allocation error). Crashing once in a blue moon in a battle isn't so annoying to me because I always save before every battle
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But now I'm in Ellinia/Undead lands and I usually can't play 5 minutes without DEP killing the game.