amavis > 'delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]: connection refused'

So on Tuesday afternoon 3 of our 10.6.8 mail servers stopped sending emails and started queueing all emails.

We looked around and evntually found that the amavis.log shows the following:

'delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]: connection refused'

Some googleing revealed some older entries on various forums where other people described having similar problems - we followed some of their advice and have since managed to get all servers going again, however we have not yet managed to find what originally caused the problem as there were not any updates installed nor anything else obvious going down that could have caused amavis to go bonkers.

If anybody else has had simliar problems and or knows of a the cause of these problems, we would very much appreciate if you could share any hints or advice.