Game freezes - lost for ideas...

[Betelgeuse]

I've been trying to figure out why SH4 keeps crashing and at wits end at this point as to the cause. The system is a Q6600, 4Gig RAM, Radeon 2900XT 1Gig on Asus P5K Deluxe - latest drivers for everything, running under XP. The game will run for a bit and then freeze with repeating sound and/or garbage on screen. This is totally random, sometimes happening soon after starting a mission, sometimes after an hour and sometimes never. I really have no idea at this point why it crashes, no other games I own seem to have this problem. I also run Vista 64-bit, does the game run under Vista? Perhaps I should try it under that OS. Thanks for any ideas....