While installing a fresh vCenter 5.1 recently I was presented with this really helpful error message at the point where you are registering a vCenter Server administrator user or group with vCenter Single Sign On:
Wrong input - either a command line argument is wrong, a file cannot be found or the spec file doesn’t contain the required information, or the clocks on the two systems are not synchronized. Check vm_ssoreg.log in system temporary folder for details.
There’s a VMware KB article which references this, but wasn’t quite my problem. Additionally it states that “This issue is resolved in VMware vCenter Server 5.1.0a”, where I was using vCenter 5.1 U1a and you would hope that the fix would be kept in for a later release ;-)
A communities post here suggested that it may be related to the SSO install option I had chosen below for HA and the fact that the group above was local not AD based:
Switching the local Administrators group above for an AD based group then permitted me to continue the install.