we had a s issue today, we could not install VSC 2.1 on Vcenter Server Windows 2008 R2 64 bit, the error message was exactly the same.
Our server is NOT MEMBER of a Active Directory Domain.
-There was no User Account Control Active
-We werde connected to the Console Session via RDP
"Run as Administrator" on the VSC-2.1-win64.exe did not work to Install the VSC successfully
After a few trials we:
Installed Java RuntimeEnviroment for 32bit Windows
and changed the Credentials for the NetApp VSphere Plugin Service from LocalSystem to the BULITIN\Administrator Account.
Then it worked fine for us.