cache lookup failed

Hi,

I'm running PostgreSQL 6.3.2 on Linux 4.1. I get the following error in
psql when I attempt to update two of the tables in my database (similiar
update on other tables work fine). Can anyone tell me what's going
wrong, or anything I can do to help diagnose the problem?

splat=> update status set version=0 where entry_id=402653541;
ERROR: fmgr_info: function 186528: cache lookup failed

PS A select on this same table works fine:

splat=> select version from status where entry_id=402653541;
version
-------
-1
(1 row)

'version' is defined as an int4

Thanks,
Lyn Finman