Strange "NOTICE".. Should I be concerned?

Hi.

I suspect that maybe this can be solved by changing some tunables, but the
problem I am seeing is that after a "VACUUM ANALYZE" on our production
database, we get the following NOTICE's:

NOTICE:  RegisterSharedInvalid: SI buffer overflow
NOTICE:  InvalidateSharedInvalid: cache state reset

Then each subsequent query on the clients which had open connections during
this time shows:
NOTICE:  InvalidateSharedInvalid: cache state reset

Maybe I need to change some configuration parameter to prevent this?  Is it
safe to ignore these?

I'm runnign PostgreSQL 7.0.2

I am running postgres like this:

pg_ctl -D /var/lib/pgsql/data -o -B 512 -i -N 128 -p /usr/bin/postmaster start

Host system is Linux 2.2.x, dual P-III's, 768 MB ram. 

Thanks for any tips anyone might have :)

Mike