When mine did it a disk wasn't loading properly. The disk was only half way in. I went to an audio repair shop and asked them about it. They said that it was probably just dirty rollers that pull the cd in. He said to take a Q-tip with window cleaner on it and clean the two rubber rollers. I didn't think that such a simple fix would solve it, but tried it anyway.
It worked and has kept the cd working ever since I did it months ago. Mine was also showing an error message on the face unit. Don't know if that is what is going on with yours or not.
BTW, I got the disk to move back into the changer so that I could pull it out by using a comb and hooking the disk and pushing it back in by sliding the comb left to right. The curvature of the disk pushed the disk back in so that I could get the stack back out and access the rollers.
If that isn't your problem try the six disc dcfish has.
dcfish, so does your changer work with the Nakamichi unit? And if so, you just plug it in and the face plate interfaces with it just fine?