Does the disc have a label on it? Or was it somehow abnormally thick? Thin slot loading drives don't like thick media.
Or, is the case slightly warped down on the slot? It's possible that the disc is trying to eject and it's hitting the metal.
Either way, if you're hearing the drive try to eject.. that's a good sign. Does it take the media off the desktop and then re-mount?
Try this... take a business card, and slide it into the slot in the middle, pointing upwards. Don't put the card all the way in. And as you're putting it in, put it angled up. And press the eject button. This way, if the disc is hitting the top, it has a way to slide out.
If it doesn't work, take it to an Apple stores. There's other ways without taking it apart, but I shouldn't go into that.