OK, If I sequester my desktop from the wireless network and run the editor and the demo simultaneously it works... which makes me think it's a Loopback issue. I know a few other people have had issues with address loopback, but in other posts you've implied that the second connection stage (internal addresses) should work in situations without loopback. Since I'm looking at a LAN-only application, any advice on forcing an internal, non-loopback based connection?
Edit: I can resolve the problem by swapping out tcpEndPoint for mFallback in TcpProtocol.cs... so it looks like the fallback mechanism must be failing somehow, since it doesn't seem to be firing on its own (and otherwise seems to work). I'll poke around a bit to see if the issue with fallback has to do with the thread not spawning correctly, or something to do with the sockets not opening correctly...