THANK YOU, ARCHEON!

No problem Tony! You've helped me out on more than one occasion, so I'm happy I could finally return the favour.

Also with an 80pin cable, it's necessary to put the master device on the end of the cable and the slave device in the middle. This wasn't so the case with 40 pin cable.
This didn't seem to be necessary. My IDE disk master is in the middle and the DVD is on the end. Seems fine to me now.

Oh, but you've good a very good chance that it will work, and will continue to work.
It's just that the official way of doing it it -as Mark also states- is master drive on the end, slave in the middle. God knows I've done it backwards myself on many occasions and most of the times it worked just fine too.
I just said what I said because I wanted to be absolutely sure that that little thing had nothing to do with your problem (because it could have), but now all is well, so : hooray!