Hi, the "Update for non-existant unit" is not a problem, it can appear when you connects to a server and receive some sync message from a unit (tank) that still is not in your list, nothing to worry about.
About the error, i have check the code, and I think there is only one possibility to end the game like that:
2007-09-15 16:48:43 Closing logfile.
There should be more messages in a normal shutdown of the game. My bet is that netpanzer is receiving a signal.
Open a terminal and run the game from it (i guess just run "netpanzer" or "netpanzer -g" to see debug messages), connect to a server and when the game exit, in the terminal window you should be able to see something like:
Received signal SIGHUP(1)
aborting and trying to shutdown.
2007-09-16 12:01:57 Closing logfile.
Maybe in your case the signal name (SIGHUP) is different, i did this one by killing the game from another terminal.
Post here once you have this information.
btw, do you know how to/are you able to compile programs?