I had a similar problem in that when I would click on the TV scenario, it would try to load and then dump me back to the orbiter after a bith without displaying any TV. In my case it was due to the MythTV packages being loaded from both the Ubuntu and Avenard repositories after a fresh install. To see if this is your issue, run:
apt-cache showpkg mythtv-frontend
If it returns two separate listings, one from Ubuntu and one from Avenard, then you have found your issue.
Also, using this command, you can check to make sure that you have the correct version installed. You want version 0.21 at least until a new version of pluto-mythtv-player comes out. Check this on your core and your MD's and also check both the frontend and the backend:
apt-cache showpkg mythtv-backend
And maybe libmyth too (don't remember if I needed to change this one...)
apt-cache showpkg libmyth-0.21-0
Next, simply remove all instances of MythTV packages:
apt-get remove --purge mythtv*
apt-get remove --purge pluto-mythtv*
And then reinstall:
apt-get install mythtv*
apt-get install pluto-mythtv*
Also, if libmyth was the wrong version, uninstall the libmyth-0.22-0 and install the libmyth-0.21.-0. If your issue is that all of your MythTV packages are 0.22, then run the above steps after removing "testing" from your Avenard repo.
If this works for you, please add it to the wiki. I was going to but it seemed like I was the only one having this issue...