SurfControl Mail Filter fails more and more often

At this stage we did pretty much all the “natural” server capacity and monitoring tests known to man but SC MailGW filter still causes us trouble and stops suddenly at random times…generally in the evening though…

Anyone experienced that already? We are now suspecting the server to SAN drivers for backup causing too much latency and snow balling effect causes SC to time out and …break but this is only speculation at the moment…