> Final possibility you aren't using a MAU cable, instead you've used a
> generic 15 pin PC joystick type cable and that just won't work.

It may, if it connects the relevant pins and is short enough.  I once
did a MAU cable with two DB-15s and some 15-condutor ribbon cable.  I
first used all the ribbon cable I had on hand (some 15-20 feet) and
tested it; I saw occasional (a few percent) errors.  So I cut it down
to about six inches and have never had any trouble with it.

Of course, YMMV.  This was in a not particularly electromagnetically
noisy environment....

/~\ The ASCII				der Mouse
\ / Ribbon Campaign
 X  Against HTML	       mouse@rodents.montreal.qc.ca
/ \ Email!	     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B