In Update Manager of vSphere Client 5.1, when you are attempting to ‘remediate entity’ to apply some patches, you get this error:
“VMware vSphere Update Manager had an unknown error. Check the events and log files for details.”
This may be because there is an ISO mounted in the CD/DVD drive of one of the VMs that will need to be vMotion’d. Removing the media by switching over to ‘Client Device’ in Edit Settings may resolve it.