Remote desktop connection over VPN - IP routing issues?

Remote desktop connection over VPN - IP routing issues?

I'm trying to get a remote desktop connection over VPN to work. The VPN connection authenticates fine, and the (Microsoft) RDC client gives an error about the machine being unavailable. The kicker is this was previously working for a day, only after I mucked about with the routing table for a few hours. (This is on a Mac, so it wasn't perhaps as seamless as Windows may be on this occasion)