What Weasel said. when inspecting the cable you may be looking for the smallest tear or kink in the cable to cause a problem. also if you're not using 80conductor cable that may cause issues as well (as the little yellow toolbubble in the screenie states).
TRy swapping the cable, let bios choose transfer mode and if you still experiance issues I woul dtake a guess at it being a failed or failing ide controller on the motherboard, however that means either replacing the motherboard, or picking up a pci ide controll ferom your favourite retailer/etailer.