Yes, I had this when I added a USB device (Logitech QuickCam Pro) that didn't have Win2k drivers. The win98 drivers worked, but would cause this BSOD on power-down. It drove me nuts until I bought a 3Com webcam that was properly supported under Win2k and updated its' drivers.
Have you added any new hardware recently? If so, check for driver updates and also check your BIOS for updates.