Backend message type 0x50 arrived while idle

Hi...

We're using an older version of PostgreSQL (6.5.1, to be precise), and we're
running into a problem where during certain inserts and queries we receive a
message "Backend message type 0x50 arrived while idle".  We've also seen
backend message 0x45.  Are these defined somewhere?  We're trying to figure
out why this is happening, and if upgrading to a newer version of PostgreSQL
might fix the problem, and I'm not finding much in the way of documentation
that gets into the meaning of the various backend messages.   Any
information you can give me would be appreciated, because this is getting
really frustrating.  Thanks.

Robin
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  Robin Wynn
  Northrop Grumman Information Technology
  Email: rwynn@northropgrumman.com
  Phone: (315) 336-0500 Ext 2247
  Fax: (315) 336-4455
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