[beiju]

I have a few more obvious-in-retrospect tips for anyone who has problems like this in the future:

Check that you're using the right cable. When FIRST switched from a Linksys to the D-Link, we forgot to make a new cable. The old one almost worked, but didn't fit snugly, so it jiggled out when we drove the robot.

If you have the parts, replace each element in the chain one at a time and see if the problem goes away. We thought we had a problem with the wiring to the signal light, but discovered it was a damaged Digital Sidecar.