cache lookup failed

I am getting the following 'cache lookup failed' error when I try to
update two of the tables in my database through psql.  Similiar updates
to three other tables complete successfully.  Can anyone give me a hint
on what I'm doing wrong?  I'm running PostgreSQL 6.3.2 on Linux 4.1.


splat=> update status set assignee=0 where entry_id=134217946;
ERROR:  fmgr_info: function 186528: cache lookup failed

Thanks,
Lyn Finman