I recently bought a Helix LT which worked fine as a floor unit but it did not want to talk to ANY computers. I checked the forums and it is not a common problem, even so most of the "solutions" were just IT voodoo. The port was intact, not loose or anything and it was not even showing up as a USB device (so would not even get as far as being a driver issue); I sent it back and got a replacement. Got the new one, connected to PC, seen in HX Edit, no issues.
The moral of this tale is that just because the main unit works, there can still be a dead USB port that was never qa'ed (seems a bit poor not to do that).