Yep, 3.1.1 and using the latest Tascam drivers. As long as I have hyperthreading disabled in the BIOS, everything's fine.
Well, not completely - the XP GUI becomes non-responsive when the computer tries to go to sleep if the unit is plugged in to a USB port. You can try to log in remotely from another networked machine via Remote Desktop - the terminal services login window comes up and you can enter your username and password, but since the GUI is dead, you can't do anything once you're logged in, not even command a restart.