VM Fails to Power On

Recently I had a strange problem.  Power off VM’s would not power on, and would give this generic error.

I found KB 1006232 and was able to power on the VM by command line, but I was still not able to power them on by directly connecting to the host through the C client.  Or using vCenter through the web and C client.  I tried a lot of things, but in the end restarting the vCenter server fixed everything.