are you getting any error readings on the face plate? Mine did this when it had a VERY bad stuck cd. I was eventually able to push the cd back in with a small thin piece of something while telling it to load. I had to live with it for a long time, though. Almost was ready to take the whole thing apart. Eventually it worked itself to a place where I could see what needed to be done, albeit barely. If there are no CD's in it at all, then I don't know... Maybe disconnect the battery for a while and pray some magic reset happens? It could just be that it has gone bad...
Let us know what you find, our cars are starting to get to that "stuff starts breaking" age and it worries me...