Actually, after shutting down several heavy programs (incl. iPhoto, Photoshop, Keynote etc.), with several large files open, the DVD Player appeared with the DVD visible in Finder. Maybe my machine just had too much on its mind?
I loaded a DVD into my MacBook Pro but it isn't recognized. Then I am not able to eject it either. It is a rather old DVD (2004), but i have noticed the same with some audiobooks. Any suggestions how to overcome this problem?