This is quite an old crustacean of a thread, however, I fixed a CD drive that had this problem (HP 9100)
Problem was that tray appeared to be frozen and would not respond to the paperclip method. So I kept at it and finally got the tray moving - the problem was that it was VERY stiff due to.... dirt, rust, ???
However, when pulling it out (or pushing it in) - I don't remember precisely, I could feel that I made it skip a couple of teeth in the tray gear train.
Now I have the problem, it won't stay open.
So I figure, I have to get those teeth back in alignment.
So I open the drive and when the tray is full out, I hold it out firmly while the mechanism is trying to retract it. Then, I let it retract (maybe I pushed it in a small distance before the could respond - I don't really know which) and as soon as it was maybe 1/4 to 1/2" in, I pulled it out skipping a couple teeth again on the gear train.
Now it works perfectly after this chiropractic treatment(!)
Of course, this method probably depends on which way I skipped the teeth in the beginning. But at any rate, the problem is that the tray gear train needed "timed" - not totally unlike how you have to position the camshaft properly when you rebuilt an engine.