I had difficult connecting to a site using Windows VPN on a machine which also had the Cisco VPN Client. They wouldn't play ball together at all. I had been connecting by going into Windows Service manager and stopping the "Cisco Systems, Inc. VPN Service" this enabled me to connect to my Windows site. I finally stumbled upon the answer! Right click on the Cisco client in the windows task bar and disable the option "Stateful Firewall Always on". After doing so I can be connected to both either VPN (or even both at the same time).