Just found a hyper-v server running at 100% on all 8 cores. Task manager showed that monitoringhost.exe was the culprit.
Monitoringhost.exe is an agent of System Center Operations Manager 2007 and is used to report back the status of a server. Stopping and Restarting the OpsMgrHealth Service cleared the problem. A little more digging found that this is a known problem and there is a patch available from Microsoft to fix this:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;954903