Weird postmaster crashes

I am experiencing database server crashes quite frequently (sometimes,
*daily*), and I am having hard time identifying what could possibly be
causing them :-(
They seem to be happenning kinda randomly, I was unable to attribute
them to any specific database activity going on at the time...
The postgres log looks like:

2003-06-10 13:53:32 [14522]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
2003-06-10 13:53:32 [16915]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
2003-06-10 13:53:32 [14523]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
2003-06-10 13:53:32 [17095]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
2003-06-10 13:53:32 [14551]  FATAL 1:  LWLockAcquire: can't wait without
a PROC structure
2003-06-10 13:53:32 [14551]  FATAL 1:  LWLockAcquire: can't wait without
a PROC structure
2003-06-10 13:53:32 [14527]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
2003-06-10 13:53:32 [14685]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
2003-06-10 13:53:32 [17093]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
2003-06-10 13:53:32 [17092]  DEBUG:  pq_recvbuf: unexpected EOF on
client connection
.... <snip a few identical messages (with different pids)

2003-06-10 13:53:33 [14072]  DEBUG:  server process (pid 14551) exited
with exit code 1
2003-06-10 13:53:33 [14072]  DEBUG:  terminating any other active server
processes
2003-06-10 13:53:33 [1609]   NOTICE:  Message from PostgreSQL backend:
        The Postmaster has informed me that some other backend
        died abnormally and possibly corrupted shared memory.
.....


It does not even produce a core file after this - just silently exists,
and restarts itself.

Could somebody please point me to any clue what could possibly be wrong
with it?

This is 7.2.1 - I know, I need to upgrade.
Working on it, but it is going to take a while, and at the time being I
would greatly appreciate any ideas on what I can do about this thing.

Thanks a lot!

Dima