Windows 7 wont restart/shutdown properly unless i unplug usb sound device first

[windows]

In xp, my Tascam US 122 usb audio interface works fine. On my windows 7 computer the device works, however when i restart/shutdown it hangs at the "shutting down" screen forever. If the usb cable is removed prior to initiating restart/shutdown then everything goes fine, the computer restarts...