Added this thread to my list of Leopold possible controller problems in my subforum.
See Lysol's post. I suspect it has to do more with the 12KRO trick they use.
This kind of behavior is an electrical issue, not a USB enumeration issue. Sorry to say Ripster, and not to detract from your self-appointed title, but your suspicion lacks SCIENCE!
As TheProfosist notes, it's not an issue isolated to the Leopold.
I have had to restart the PC in order to get the keyboard to work this has happened mostly with my HHKB though so I dont think that it is only a leopold thing.
USB is a shared bus, and in order to maintain current/voltage to other devices on the bus when a new device is plugged in, each port of a USB master controller has it's own over-current switch (resettable fuse) which can be triggered by a short or a device drawing too much current. Given the small distance between pins on the USB mini-B connector, it's not a surprise that a short could occur on occasion, particularly given the somewhat unnatural angle of insertion required with a Leopold.
Admittedly, the likelihood of a short with the mini-B somewhat diminishes its convenience, and in my limited experience, mini-As do better in this regard, but they lack the structural strength.