Try to boot another machine with Knoppix and conncet the USB drive there. I have had many USB dispositives.

1 Usb 1.0 64 mb thumb disk Cigarr Pro, work flawlessly
1 Usb 2.0 128 mb thumb disk Apacer, no way in Linux
1 Usb 2.0 256 mb thumb disk gneric, no way in Linux (appears in the desktop but the system was unable to read it)
1 Usb 1.0 IDE enclosure generic, no way in linux
1 Usb 2.0 IDE enclosure generic, work flawlessly

So, is a tricky task. Some USB work without a glitch, another need more work