I stumbled across the same issues... as far as MythVideo goes, try this:
...assuming apt is configured as per default, and you are running 64bit. If you are running 32bit you will need to provide the correct deb.
sudo dpkg -i --force overwrite /var/cache/apt/archives/mythvideo_0.20.99+trunk15283-0ubuntu0~mythbuntu1_amd64.deb
MythStream on the other hand had to be compiled from source, and is still kicking up some issues... segmentation faults on exit causing the frontend to crash.
sudo dpkg -i --force overwrite /var/cache/apt/archives/mythvideo_0.20.99+trunk14583-0ubuntu0~mythbuntu2_i386.deb
Hope this helps,