In the process of fixing that problem I accidently set the date forward to 2010-08-07.
Even though the problem was correctly in a manner of minutes, it appears all service checks were performed in the future.
If I "Schedule an immediate check" then the next check date changes to the real date/time. This service continues to get back to a regular schedule.
Now it appears that no checks are being performed, the server sees that the next check is in August.
The seems likely as I can see the Nagios XI server isn't consuming nearly as much CPU since the accident.
How do I force all hosts/services to perform a check immediately?
If there is no quick/easy solution I can revert back to the VMware snapshot I made before I installed the upgrade (and not make the same mistake again)