If you've upgraded from Windows XP Pro to Vista Business, AND you've changed the listening port of your Remote Desktop connection, AND after the latest round of Windows updates you find that it is not working, guess what? It seems that the last round of updates either enable a disabled Windows Firewall, and/or disabled or deleted additional ports in Windows Firewall. I'm not sure which, because I wasn't sure if my firewall was turned off before.

So, check your firewall settings to see if it has been turned back on, and check the exception list to be sure that the Remote Desktop port is enabled.