Can't answer the question directly, but just wondering if you are able to open regedit and connect remote registry or if that is also blocked?
If it's not blocked, you can connect network registry and browse to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server key on the remote server (need to connect with admin privileges) and modify the TSUserEnabled (set to 1) and fDenyTSConnections (set to 0) values.
This may allow you to RDP into the machine and see what's going on. Completely external to vSphere, but maybe worth a shot.