Comcast DVR 3-Device and Panasonic Home Theater

Did you unlock the volume keys for AUX (or what ever device the home theater is set to)?

If the TV button is flashing when you press volume buttons while in AUX mode or CBL mode that means the the remote is set to send volume control command of the TV no matter what mode you are in. To unlock it for one device (I'm assuming you have the HT device on AUX button), here's the instruction from the manual.

Unlocking Volume Control For A Single Device (Individual Volume Unlock):
1. Press AUX
2. Press and hold Setup until the selected mode key blinks twice, then release Setup.
3. Enter 9 - 9 - 3 and then press VOL- once.
The mode key will blink four times confirming unlock.

Now, when you press vol keys in AUX, AUX button should light up.

By the way, if you want to use other keys besides volume and power, other device codes might be better, depending on which model of HT you have, so what is the model number?

[EDIT] I see you already found the instructions while I was typing. I hope that worked