My Superdrive on my 24" iMac stopped working some time ago. The optical drive just vanished, not showing up in profiler, Disk utility or anything. Then I got it replaced (they actually had to do it twice), but the new one only worked for a couple of days before it stopped working again. Then I gave up and bought a USB2 Samsung WriteMaster external DVD-burner. It worked well for a long time, but now suddenly my external drive does not appear any longer. Anyone else got problems with external DVD-burners not showing up when running Snow Leopard 10.6.3?