I am having a similar issue. I have 2 Dell Latitude 6420's. They have Centrino 6205n cards in them. The users are able to connect to the VPN using Cisco VPN client but for whatever reason, the client machine uses the external DNS server rather than the VPN network DNS servers so they are unable to find anything (mail servers, intranet site etc) on the internal network.
Any other client machines that do not have Intel Centrino cards are fine.
Very strange issue......