The problem is you have the wrong drivers install
remove the v4l2-modules and install v4l2-ngene-modules
currently the version of myth that i have out now doesnt have good DVBS/S-2 support.
im looking for a few people with S/S-2 cards to test some new drivers, i will be releasing with an update to myth
hit me up in irc and lets test some stuff
Thanks
Mandingo