Cisco VPN client, ISA firewall client + RDP

Hello

I have ISA 2006 with all machines using the firewall client. An application used in the company requires a cisco vpn client v 4.8.00. I have a rule that allows all outbound traffic to the vpn endpoint and that connects without trouble. However when I try to use RDP over the VPN I have to a) disable the firewall client or b) include the remote network in my internal network on isa so the client doenst pick it up.. I am not happy doing things this way.. Does anyone know why this is happening.

Thanks in Advance