Please confirm that we correctly understand problems you are experiencing.
Problem with hanging connection without even getting a auth dialog happens only when connected via VPN?
When connected directly connection is authorized but session not displayed, disabling UAC fixes that and
you can start session?
When connected via VPN can you see Windows Login Screen but after providing credentials it hangs?
Next time you connect via VPN a session fails with ‘Error is 5: Input/Output Error’ ?
Can you correctly start a session when connecting directly, without VPN?
Can you tell us what kind of VPN are you using?