I'm currently running into an issue where the frontend can't connect to the backend. The problem is related to the IP addresses that get defined in the mythtv-setup->General section. By default, LinuxMCE sets the first IP address to the IP of the internal network. The second IP field is being set to "localhost". This mismatch is an issue.
According to the how-to document at mythtv.org you either need to have both IP fields set to localhost or both fields set to valid IPs.http://www.mythtv.org/docs/mythtv-HOWTO-9.html
"NOTE: If you modify the 127.0.0.1 address and use a "real" IP address, you must use real IP addresses in both fields, otherwise your frontend machines will generate "Unexpected response to MYTH_PROTO_VERSION" errors."
To fix the problem I have to manually run the mythtv-setup EACH I start LMCE and change the first IP to localhost.
This was initially working, but it broke somewhere along the line. My guess is that it stopped working when I changed the network settings for my box from within the pluto admin pages. I currently have my box setup with a static IP and I let my router act as the DHCP server for the rest of the boxes on my network. There must be a bug where the changes that I made aren't being reflected correctly in the mythtv setup. Is there a place in the Admin pages where I can change the IP value that gets used in the MythTV setup?