We encountered issues that mysteriously appeared after a patching window on our vCenter server. We had just upgraded to vCenter 4.1 earlier in the month and this was the first time the server had been rebooted since the upgrade.
After reboot, the Last Updated timestamp on all datastores was stuck at the time the vCenter service came online. None of our disk space alarms worked because the datastore statistics were not being updated.
We noticed that the problem only appeared on the 4.0 U2 hosts – datastores connected to 4.1 clusters had no problem.
VMware support acknowledged the timestamp update issue as a problem in 4.0 U2 that was partially addressed in 4.1 and fully addressed in the soon-to-be-released 4.1 U1