On closing the tray it immediately reopens, with or without a CD in the tray. BIOS and Windows recognise the drive but cannot read it (the tray does not stay closed and I cannot hear the drive spin up).
After closing the tray the drive light comes on, but does not flicker, then goes off when the tray reopens.
This happens on two modern machines, one a P4B running Win98SE and the other an Athlon running Win2000. I have also tried the drive as Primary Slave and Secondary Master with the same results.
I have confirmed all jumpering and cabling to be correct.