I'm having this exact same situation out of the blue and have been troubleshooting my butt off. Came to the forums because I have a hunch a Windows update may have flubbed something up. Only reason I suggest this is because this configuration has been working, then poof... have this issue on two separate computers.
I decided to check the forums to see if anyone else has been having the same situation recently and lo and behold found this thread.
I have a MK2 for the record.
In device manager, it shows under USB devices Unknown USB Device (device descriptor request failed)
Two different machines, different cables, same results.
I've tried pointing different drivers at it with no avail, and also making sure that driver enforcement is turned off.. Not trying to hijack Archer's situation but they seem pretty similar and unique to immediately think it's a coincidence (although it may be).