Should be a problem right, as long as they not both being used a once?
I'm running 2 BenQ 1620s on the same IDE cable, and I have not had any problems. I haven't tried burning with both at the same time, but I've heard it can be done â€” though it increases your risk of getting coasters.
I've got four burners on both IDE cables. Have my harddrives on a Promise Ultra PCI raid card and have no problems at all.