A previous admin set up Nagios to provide a lot of alerting before he left. It's all good and helpful. However, one server neglected to respond to an email at a specific hour--04:01--and for eight days now Nagios keeps sending out Critical warnings that it hasn't heard back from that email. It's heard from every email before and after that time, but it hasn't heard from that specific email. So, we have no problem, we just need to tell Nagios to stop notifying us about that one stale alert but continue checking for future alerts. Unfortunately, I don't know enough about Nagios to tell it that.
We are running version 3.2.0 of Nagios on RHEL 5.5.