Pansonic defaulting to aux instead of D-IN 1

Kim,
Thank you for your responce
There are two setups both with the same problem
first is:
TV Panasonic vieta 55" plasma connected to a Panasonic SA-BT300 7.1 Bluray Home Theater system.
Dish Hopper S230 NACD HD reciver and DVR.
the symtem is aferter turning the system on the sound cut out and the system failes over to AUX. you then have to press the EXT-in on the remote to have it switch over to D-IN 1.

The second system is
TV Panasonic vieta 47" LED with a SU-HTB20 sound bar and is connected to a Joey
It too comes up and then fails over to AUX.