Not sure about Vista, but I had to create a firewall exemption in XP SP2 in order to get RDC to work via my VPN. Have you checked your firewall settings?
Security with ease of use is the promise of Secure Sockets Layer VPNs. In our test of seven SSL VPN gateways – from AEP, F5 Networks, NetScreen Technologies, Netilla, Nokia, Symantec and Whale ...