Remote Desktop does not work to TMG (ISA) server

If all rules are in place for RDP, but you still can't connect to your TMG (ISA) server, following steps might help you:

This is for Windows Server 2008 R2

Connect to TMG locally and go Administrative Tools -> Remote Desktop Services -> Remote Desktop Session Host Configuration

In connections table right click RDP-Tcp and select Properties then select Network Adapters tab and choose Network Adapter: for which you want to enable RDP.

Links: http://social.technet.microsoft.com/Forums/en/Forefrontedgegeneral/thread/ef37e149-27ce-4da9-8739-cc58fdba46dc