No forget about the drivers I mentioned, was just thinking out loud really, some really old games would only run on new age systems with certain drivers from the pre Windows XP era, like OpenGL etc which I think is about the time of Windows 98. But as the game does run on your system and wikipedia says it supports XP in 2003 then it cant require these otherwise the game would refuse to run at all.
Very strange how the game will run fine until you load certain maps you mention?