My 20" iMac isn't recognizing blank DVDs for some reason. They don't show up on the desktop or in Finder, and I have to reboot the computer with the left mouse button held down just to eject the blank. This is especially puzzling because I have not had this problem before with this machine - I've already used DVDs from the same package to burn things before. Is there something I should be doing in Disk Utility or somewhere else to get it to recognize blank DVDs?