We don't officially support USB 2.0 drives. If you disconnect this drive, do you have the problem when using the internal hard drive with a single audio track?
Another user found he had to disable the "Microsoft ACPI-Compliant Control Method Battery" in the device manager to relieve CPU errors in this thread.
http://duc.digidesign.com/showflat.p...part=1#758239]
regards,
Digidesign Technical Support