I am using to 6GB/ Sata Slots for 2 HDD a WD320GB Blue and a Green 2TB, just bought a CD.RW but because i only have two 6gb ports so i put it in the 3gb port and nothing its doesnt come up as pluged in for refrence am using a ASUS P8H67-M
Plug one of the drives into the same port you plug the cdrom in to and see if it works if it does then the port is ok,
Then test the cdrom in another machine could be DOA cd drive.
if the drive works - default the bios and try it all again. nothing worse then a wrong setting to send you hunting for faulty components.