Hi Foxman and
I had a similar problem a few weeks back when exchanging a dvd rom for a dvd writer
Sometimes it was there and sometimes not. Have you go the bios set to auto detect for master and slave on both ide channels ?
It seemed to be something to do with the PI0 mode settings, after setting the cd writer and the dvd writer to 0 it found both and indentified them correctly ever since.
Not sure if thats the same as your problem but I know it was frustrating as I had swapped ide leads and jumper settings, had each as master and slave alternately