fatal error in pg.log

We are using ver 7.3.4 (old I know but we can't upgrade until early next
year) on a linux 2.4 system and are having some flaky problems with our
apps. They just die at apparently random times. In trying to figure
out what is going on I noticed a couple of messages in pg.log that
concern me:

FATAL: unsupported frontend protocol

WARNING: Message from PostgreSQL backend:

The Postmaster has informed me that some other backend

died abnormally and possibly corrupted shared memory.

I have rolled back the current transaction and am

going to terminate your database system connection and exit.

Please reconnect to the database system and repeat your query.

Can anyone tell me what these mean?

Medora Schauer

Fairfield Industries Inc.