It sounds to me as if you've lost your DVD in some way, although having it as master, I would have thought that the slave would be knocked out as well. Check your data cables on the DVD - both ends - take them off and replace them, checking for bent pins. Try a different power connection. Also check the jumper is correctly set. I assume that your BIOS is set up to see the DVD - double check. If all else fails, I would imply that the DVD has met its maker.