Rob, Thanks for your response!
To answer your questions...I have both a Happauge PVR 500 and a Happauge PVR 150 installed.
My media menu choices are (in regards to this problem) Live TV and Live TV STB. If I select Live TV I can view my STB programming, record, rewind, pause, FF and view the program guide with LinuxMCE BUT it will not change the channels on my STB.
If I select Live TV STB then I can change the channels on the STB but not record, pause, rewind or FF. If I attempt to rewind etc. It gives me button Icons to click (essentially sending an IR signal to tell the STB to rewind etc.
I have tried using all three of the inputs on the cards.
I have ran MythTV setup more than a few times. Can you tell the best way to get the STB to change channels AND have Mythtv PVR capabilities. I am willing to start at square 1.