Hi
I had a similar problem for a while where it wouldn't respond to the source buttons though there was light in them. But when I activated them with the remote the other functions worked. But it was temporary and sometimes they did work.
I am not sure what fixed it, but after a while the problem stopped, but around the same time I had a problem with the laser in the CD player. I had it in for a repair and they told me the replaced a fuse resistor (not sure if that is the right translation). Anyhow I don't kno it that has anything to do with it.