EMC10 uses a system that Roxio called the PX Engine to recognize and link with your optical drive(s). I think yours may have been broken by something.
Please read this topic. Start at the 6th message on that thread, written by Guru cdanteek, and follow his instructions precisely. His message contains a zipped PXEngine installer, and instructions on how to run that installer with the "/pxhelponvista" parameter. (Even if you're not running in Vista)
Using this to reinstall your PX Engine should fix your problem. It has helped a large number of users.