On 5 Nov 2011 at 21:49, Jules Richardson wrote:
  I've got a converter which I use to connect
my Model M - oddly enough
 I've seen the same sort of behavior that Mark hints at, in that very
 occasionally the system will seem to think that a key has been held
 down, and will cough out repeat keypresses. 
 You may want to peek inside to see if there are any active devices in
 your converter.  Most are purely passive--and there's the rub. 
How could a purely passive converter possibly work with an original Model
M? Surely a USB port is not going to accept the clock/data lines of a
Type M on its differnetial data line pair?
-tony