I've been a satisfied Digitrax user for nearly 9 years. Initally all my loconet cable were made up by one of the local agents here in South Africa obviously all of these were tested prior to installation on the layout. I once I experienced loss of communication in a sperate power zone, and this was tracked down to a failed UP3 (now UP5), which was replaced. I have subsequently made up loconet cables, using a crimping tool from Maplin's without problems. I agree with the Lancashire Fusilier, that the problem probably exists with the loconet cable and this is where I would initally look for problems using the loconet tester provided by Digitrax. If this indicated no problem and all other loconet connections work normally, then investigate the UP5, possibly buy another one as they are not expencive, doing this as a last resort !