Had the same problem here. Unfortunately, it's entirely due to Creative's bad drivers. The release notes on the most current ones claim to have solved the problem, but they most certainly did not.
The only real solution, without hunting down custom drivers is to take out a gig of RAM. Creative's X-Fi drivers, in both vista32 and vista64, will cause you to get a BSOD randomly if you have 4GB RAM or more. The only solution is to use the Auzentek(sp?) card that has the X-Fi chipset, if you want to get the same sort of sound card.
If you
do happen to track down some custom drivers, let me know... 'cuz I want 'em.
Sorry.