Are you mounting your mybackend computer media folders?
If not, on your backend box, set up nfs to share the recordings, music, video, etc. directories.
For example I keep all those directories in /home/mythtv/
then on your frontend box use nfs to mount those directories in the same location
e.g. on frontend
mount 192.168.x.x:/home/mythtv /home/mythtv
I was confused when I set up a remote fronted becuase the fedora mythtv howto did not say anything about nfs.