Unfortunately the news isn't good. If your TV is responding to the power commands but not the input commands, chances are you have an older version of the firmware. To check the firmware press the following buttons in order carefully: With TV on, press Power-mute-1-8-2-power. This will bring you into the service menu. To exit this menu, turn the TV off for 30 seconds. On the bottom of the screen is a long number. The last 3 digits of that number is the firmware version. Versions 214 and higher have discrete input selection, while 209-213 only have discrete power. Chech this out first we can go from there.
DO NOT make any changes to the setting in the service unless you know exactly what you are doing. Changing things in the menu can result in a dead TV.

Jason