I have a Nuvi 350 connected to a Tracker 2 but it's not a permanent connection (sometimes I disconnect the GPS to use as just a portable GPS). The other day I was testing it and I couldn't get it to communicate with the Tracker 2 after it had been working in prior tests. In my case, it turned out that I had the power and comm connectors mixed up (they look alike at the GPS side).
The power connector must go in the back through the mount and the comm cable must go in the side (the same one used by the battery charger). Reconnecting the cables made everything work like it used to. I could send and receive messages, get waypoint updates, etc. I don't know if that's what's happened in your case, but your symptoms sure sounded familiar when I read them. Good luck with the troubleshooting! --bob K7RBW
