Sounds likely. Before your VPN comes up, the prospective client and the VPN server have to be on different IP subnets. Otherwise when the VPN comes up and the client receives the psuedo-NIC that the VPN creates, the IP address of the psuedo-NIC will be in the same IP subnet as the 'real' NIC and the poor PC won't know which interface should be used for the VPN traffic and which for the normal. That's why it doesn't work
