there should not be any difference. i host jo:ic on my old xp machine and that is 32 bit and have not seen any issues like that.
maybe the difference in how the map editor was coded could cause that. ex: the c4med for df2 has an issue with the different heightmap calculations when using a df2 terrain in wireframe.
maybe we can set something up where i put your maps on my xp machine and then go in to see if there is a difference?