Tim Helton, a Senior Supoport Escalation Engineer in our North Carolina office, recently posted a cool utility that will reset all of the health monitors on a single agent or all agents so that you can get re-alerted on all current issues even if you've already cleared them in the past.
Per Tim, "This can be very useful if you just had an event storm, and you want to reset everything back to "green". It also has the ability to identify "ManualReset" monitors, and reset or recalculate only them."
To read more about Tim's utility and to download it see http://blogs.technet.com/timhe/archive/2009/01/15/announcing-the-greenmachine-utility-for-operationsmanager-rtm-sp1-and-r2.aspx
J.C. Hornbeck | Manageability Knowledge Engineer