I have had the same problem with DEP error as a lot of posters on this forum. After reaching Demonia the problem got so bad, occuring every couple of minutes. I have however managed to solve this problem now it seems, and have finished Demonia, and have been playing stable for 3 hours. The solution that worked for me is to turn off DEP in vista (32 bit) this way:
Type cmd in Vista's search bar. Rt click on search results 'cmd' and click on Run as Administrator. Then copy paste
bcdedit.exe /set {current} nx AlwaysOff
and hit enter. Reboot.
To enable back DEP, type instead:
bcdedit.exe /set {current} nx AlwaysOn
Thats it !
Hope that this also will solve other peoples problems. Hopefully turning DEP off will have no other (bad) consequenses.
Hopefully there will be a patch soon that will incorporate a permanent fix for this wonderfull game.
KINGKNUT