Most common mistake today is to not use 80 connector cables right... since they tend to ship with all new motherboards anyway and people buy them because they are "better"
First, you don't need 80 connector for non-HDD ATAPI devices. This is because only HDDs are going to be faster than ATA66 and the 80 connector cable is only required for speeds above that.
Second, the cables ARE actually keyed on the 80 connector versions. BLACK is master device, GREY/WHITE is slave and BLUE/YELLOW is the ATAPI controller header. The drives should be set to CSEL (cable select) but will work fine, usually anyway, explicitly jumpered as master and slave.
Obviously also make sure you seated the connectors properly, did not bend pins, and so on.
SOMETIMES, CD-R/W drives seem to not work unless they are the master; since you lose nothing by making the DVD-ROM drive slave instead, give that a go too. It ought not to matter, especially on modern controllers and modern ATAPI drives.. but I have encountered it.
