Connection question

I have a two-user point-of-sale application on Windows XP PRO. The DB runs
on the cash register. The second user is a manager's computer. They are
connected through a wired router which is also connected to an internet
cable modem. The manager's computer just checks statistics on the DB and
maintains a connection all the time. The cash register application does not
do any network operations and is not even aware of the network.

About twice per month, it is necessary to reset the modem and router. This,
of course, loses the manager's connection to the DB. The problem is, it also
seems to break the connection at the cash register. The next time it tries to
record a transaction, it gets the error "Unable to write to the backend" or
something very close to that. The DB itself seems fine as we can restart the
cash register and all is well.

Anyone have any idea why this happens? We are running PostgreSQL 8.3.1-1
and the applications are Java 1.6.14.

Bayless