Incomplete Startup Packet on startup and when pg_maintenance --analyze runs in cron

Running Ubuntu 8.04 LTS, with postgresql-8-3, postgresql-client-8.3,
postgresql-common - standard Ubuntu stable postgresql package. The same
error occurs on a system with postgresql-8-2. Both boxes are also running
python-psycopg2. Connections limited to localhost. Nothing monitoring or
scanning port 5432 at a 5 hour interval.

I'm get the following error in the logs at startup and at the exact interval
that -x /usr/sbin/pg_maintenance ]; then /usr/sbin/pg_maintenance --analyze
appears to run in cron:

From /postgresql-8.3-main.log :

2008-12-17 00:02:01 PST LOG: incomplete startup packet
2008-12-17 05:02:01 PST LOG: incomplete startup packet
2008-12-17 10:02:01 PST LOG: incomplete startup packet
2008-12-17 15:02:01 PST LOG: incomplete startup packet
2008-12-17 20:02:01 PST LOG: incomplete startup packet

Verbose on startup:

2008-12-18 12:15:48 PST LOCATION: StartupXLOG, xlog.c:4816
2008-12-18 12:15:48 PST LOG: 00000: autovacuum launcher started
2008-12-18 12:15:48 PST LOCATION: AutoVacLauncherMain, autovacuum.c:520
2008-12-18 12:15:48 PST LOG: 00000: database system is ready to accept
connections
2008-12-18 12:15:48 PST LOCATION: reaper, postmaster.c:2156
2008-12-18 12:15:49 PST LOG: 08P01: incomplete startup packet
2008-12-18 12:15:49 PST LOCATION: ProcessStartupPacket, postmaster.c:1396

From /syslog

Dec 17 00:02:01 nameofserver /USR/SBIN/CRON[26124]: (root) CMD (if [ -x
/usr/sbin/pg_maintenance ]; then /usr/sbin/pg_maintenance --analyze
>/dev/null; fi)
Dec 17 05:02:01 nameofserver /USR/SBIN/CRON[1879]: (root) CMD (if [ -x
/usr/sbin/pg_maintenance ]; then /usr/sbin/pg_maintenance --analyze
>/dev/null; fi)
Dec 17 10:02:01 nameofserver /USR/SBIN/CRON[9264]: (root) CMD (if [ -x
/usr/sbin/pg_maintenance ]; then /usr/sbin/pg_maintenance --analyze
>/dev/null; fi)
Dec 17 15:02:01 nameofserver /USR/SBIN/CRON[15886]: (root) CMD (if [ -x
/usr/sbin/pg_maintenance ]; then /usr/sbin/pg_maintenance --analyze
>/dev/null; fi)
Dec 17 20:02:01 nameofserver /USR/SBIN/CRON[12183]: (root) CMD (if [ -x
/usr/sbin/pg_maintenance ]; then /usr/sbin/pg_maintenance --analyze
>/dev/null; fi)

This seems like a missed configuration option -- but I'm not sure where.
Any ideas?

Thanks,
Jennifer