I don't think that the IDE cables were incorectly installed (I think they will only go in one way), however, there is a good chance that the cdrom is sharing an existing IDE cable with another device. If this is the case, then It is possible that both devices are on the Master setting. Change the cdrom jumper to slave, and it should correct the problem.

This may not be a problem, I am merely guessing.

--Sudo