You can check the screws that you installed under the keyboard (just on top of the optical drive) if they are too long they will prevent the PowerBook from ejecting the CD. That is what happened to me. You really have to be careful that you put in the right length of screw. If it is just a little bit too long the CD will insert easily but when trying to eject it will catch on the screw (particularly the center one, the ones on each end aren't as critical) and get stuck. Try removing just the center screw. I'll bet that you will then be able to eject the CD.

gwrivest