loosing connection with serial port connection

RedHat Linux 5.1, PostgreSQL 6.3.2.

Are there any special considerations for running a libpq app from a
terminal hung on a serial port? This app runs fine from a local console,
but dies shortly after starting on a serial tty. What I mean by dies, is
that after some initial queries to the backend (successful) further queries
will result in an error, 'No connection to backend'. A ps still shows the
postgres process as alive.

The postmaster startup is: /usr/bin/postmaster -i -S -D/var/lib/pgsql
The postgres process is: /usr/bin/postgres -p -Q -P5 -v 65546 databasename

Thanks,

Ken