HA Errors after vSphere 4.1 Upgrade

I recently ran into an issue with one of my vSphere clusters after upgrading from vSphere 4.0 to vSphere 4.1 (with ESXi 4.1 and vCenter 4.1).  After the upgrade, I attempted to enable VMware High Availability (HA) on the upgraded cluster.  Each of the ESXi hosts in the cluster appeared to have been properly configured for HA (as observed in the 'Recent Tasks' pane of the vSphere Client).  Despite having appeared to configure HA correctly, I found that each host in the cluster was displaying an error on the Summary tab of the vSphere Client that read 'Error <date> <time> HA agent on … [Read more...]