OK. So there are solutions to this online, but it took me a long time to find them so I’m going to add one more here. The problem is that you are using a PPP adapter to connect to your LAN, but when you try to resolve internal names that have both and internal and external address, you keep getting the external address.
The reason this is happening is that windows is preferring the DNS from your home connection to the one from your VPN. Normally you would change this by going to Control Panel->Network Connections->Advanced (drop down menu)->Advanced Settings. In the “Adapters and Bindings” tab you can change the order of preference for your various connections. Unfortunately with VPNs this doesn’t actually work. It turns out you need to go into the registry to fix it. (NOTE: you have to reboot after changing the registry because even though nslookup will now work everything else will not).