This was discovered during an upgrade to one of our VC servers to update 3. We attempted to install VUM and received a cryptic error about failed registration. The install worked fine in our lab VC. We learned that the plugin installation does not utilize the local adminstrator group on the windows server you are installing on, but uses the actual VC permissions instead. The core VC installation portion requires the installing user to be part of the admin group on the windows server you are installing to, but the plugin install looks to the VC permissions list. We input the user into the administrator's role in VC at the root folder and all worked.
This will not affect those who did not remove the administrator's group from the VC administrators role after your initial VC install - which I consider a best practice to remove! FYI - the reason it worked in the lab VC is because the local admin group was not removed from the VC in the lab.
