Hi cartworld,
The first question I would like to ask is, which environment are you trying to boot into? I would also like to know if the USB device is accessible if you use another computer running in Windows?
If you are attempting to use Service Center DOS for testing, some systems have been found to have difficulty reading the USB device for authentication when booting from the CD. If this is the case, I would recommend that you boot from the USB key instead.
If you are testing with Bootable Diagnostics, then it shouldn't matter which environment is used to boot. The only issue we have found with reading from the USB device is that adding or removing the key during the boot process can cause errors. If this is the method you are using, I would recommend either booting from the USB key or waiting until the software loads before connecting the key.
Please let me know the the answers to my questions, and if either of my suggestions help at all.
Thanks,
Kris