FATAL: could not read statistics message: Connection refused

Hi,

I recently came upon this error message on one of our 8.1.1 server :

FATAL: could not read statistics message: Connection refused

Any ideas on what could possibly be the cause of this ?
Some search on the lists shows a similar error :

FATAL: could not read statistics message: Resource temporarily unavailable
(http://archives.postgresql.org/pgsql-general/2006-05/msg00752.php)

Which seemed to be due to some buggy kernel settings. Are those two
related ?

Thanks for your help,
Nicolas Lê.

postgres=# select version();
version
-------------------------------------------------------------------------------------------------
PostgreSQL 8.1.1 on i386-unknown-freebsd5.4, compiled by GCC gcc (GCC)
3.4.2 [FreeBSD] 20040728
(1 row)