Intermittent occurrence of ERROR: could not open relation

I have been running PostgreSQL 8.4 on Windows Server 2003 Service Pack 2 for almost 3 years. I have recently been intermittently getting the error "ERROR: could not open relation base/85599592/121526263: No such file or directory". It only appears to be happening during the execution of stored procedures where an insert into a temp table is performed. The error goes away after the user reconnects with a new session.

This database periodically gets copied to a PostgreSQL 8.4 server on a Linux RedHat 4.5 machine where the same error also has started intermittently occurring; again it only appears to happen during the execution of stored procedures where an insert into a temp table is performed.

Does anybody have an idea what might be happening? Are there any config settings for temp tables that might help prevent this error? Any help would be much appreciated. Thank you.

Andy Nykolyn
Northrop Grumman