vCenter Alarms not triggering

I’ve recently just finished upgrading our vSphere environment from ESX4.0 to ESXi4.0 and encountered a strange issue with alarms.  We have custom alarms for when a datastore is overprovisioned and when a snapshot exists.  When building our two new vCenter 4.1 servers I configured these alarms so they were ready for when I connected the ESX hosts ready to rebuild.  Once I connected all our ESX hosts and add the VM’s to the inventory none of the alarms would trigger.  I knew we had datastore’s that were overprovisioned and I also created a snapshot for a VM to see if the alarm would trigger.  None of the custom alarms would trigger.  In order to resolve this I had to go into the alarm definition, disable the alarm, OK the command and then re-enable:

Obviously this had something to do with me creating the alarms before having any VM to apply it to.  Just something to watch out for.