I have an Ibanez with a Floyd Rose bridge. I was tuning it with the fine tuning pins just now, and one of them didn't work. No matter how much I spun it, it didn't change the pitch of the string. Can anyone help me fix this?
Is it all the way up? if it is then it won't be able to go anywhere. Try loosening the locking nut and tuning the string down, then put the fine tuner at ~1/2 in. Then tune just flat of the note, lock the nut and try the fine tuner again.
If it just keeps spinning and spinning then it sounds like its stripped. You should be able to turn it so you can screw the screw all the way in and it stops/bottoms out, and also screw it all the way out. If it is not doing either of these things then the threads are stripped.

Otherwise, follow swilcox's suggestion.