[aklego]

Normalmutant, your programmer is correct. Try putting the module on your robot and establishing a connection with the FCS. Without starting a match, shake your robot and see if you can get it to drop its connection. Now try the same thing but with tele-op running. The FIRST rep at our event indicated motion induced drops are much more likely while the NXT and samantha are actively communicating, and my experimenting has shown that to be true.

From the info in this thread, it seems like there is not a single problem but, rather, problems that manifest themselves in nearly the same way:

Network interference--dropped connection
Poor power connection/wiring problems--dropped connection
Manufacturing defects in power cord (rare?)--dropped connection
Low battery (FCS initially reporting green)--dropped connection
Loose USB cord--dropped connection and/or locked up NXT
Bad solder joints--dropped connection and/or locked up NXT
Programming/firmware bugs--dropped connection and locked up NXT
Others?