[OT] Flushing Postgres Function Cache

Greetings,

In the face of shabby google results, I hoped that someone hear might know
something about the postgres function cache.  We have a server which
reports an error of the form "cache lookup failed for function <oid>."

Initially, I'd hoped to resolve this without a restart (which didn't do
the trick either), and had been searching for some way to clear postgres'
internal function cache - I think it stores plans/hints/compiled-version
relating to stored proc's?

I tried to select the reported oid out of pg_proc, which resulted in an
empty set.

I then went on to explicitly drop the function and recreate it.  This was
interspersed with numerous postgres restarts and dropping of all client
connections.  In spite of this I still get the same error from our client
which still reports the same OID; which doesn't exist in pg_proc.

In any case, I can't seem to find any documentation which tells me how
to clear this cache.

Versions:

pg: postgresql v 8.0.1-r4
os: Gentoo Linux/Kernel 2.6.12.5 #1

Any help would be of value?

Cheers,

Raf