ALTEK AC40

Hi,
I'm in the process of getting an ALTEK AC40 digitizer running with grass4.1.
It works only half, that means I'm getting the message

read error from digitizer, continue (y/n) <

After pressing a key on the digitizer and answering y I can continue, but
the message returns constantly.
Does anybody have an idea how to solve that problem.

Stefan Jaeger
USGS
sjaeger@resdgs2.er.usgs.gov