I am developing a usb device driver and I got a BSOD during DTM testing with Vista SP1. This does not happen with XP. The blue screen is caused by Bug Check code 9F - the Driver Power State Failure. The four parameters 0x00000004, 0x00000258, 0x00000000, 0x00000000. When I checked the Parameter 1 values for 0x9F, I don't find 0x00000004 at all. Am I missing anything? Please help.