eried:
OK, thanks, easy to solve (skip "wrapper" if -cusbasp -Pusb used)Will post version 1.0.1H in a couple of days with the fix.
Excellent! Thanks for this. 
Perhaps this might also be a problem with other devices that don't appear as COMxx serial ports? If this was the case, maybe the more general workaround would be to apply the wrapper only if a COM port is actually specified in the avrdude command line? (Just a suggestion.)