I am currently logged into a SOHO network on 192.168.1.0/24. I have a VPN established through the normal Apple method (System Preferences / Network pane) to a remote system whose addresses are on 192.168.128.0/24. The services are ordered such that the VPN appears first.
Every other tool on my Mac (Safari, Network Utility, ping, etc.) immediately routes requests to 192.168.128.10 correctly. However, Vine Server refuses to open a VNC connection to this address, claiming that the network is unreachable. OS X screen sharing has no trouble opening a session to this same machine.
I tried quitting and restarting Vine Server, in case it fetched routing rules only on startup, but it didn’t resolve the problem.