Do Comcast have a different box with different codes or assignable code groups on either device?

I/R routing via RF receivers from the remote if you have the capability. Fixed similar problem myself this way when Marantz amp and NEC plasma shared some codes. Used Direct I/R to TV and RF extender to concealed amp.

Use cheap amp for volume if possible, can TV speakers be wired to an amp?

Are there other devices in the system? Can you use Comcast for volume?

Simon.

Screw that! Give him Dave's speech and just sit back. That places it entirely in his lap, where it belongs. You might tell him along the way that you're tired of hearing excuses as to why he won't face up to you about how he screwed up,too.

Bravo Dave!