Alvaro,
>>> - do an UNLISTEN if possible
>> Yes, we're issuing unlistens when appropriate.
>
> You are vacuuming pg_listener periodically, yes? Not that this seems
> to have any relationship to your problem, but ...
yes, autovacuum should take care of this. But looking forward for
multiple-workers in 8.3 as it should help us during high load periods
(some tables might wait too long for autovacuum now - but it's not that
big problem for us...).
Thanks for great work!
Kuba