I had this problem with the Monster cable that is "supposed" to work with an iBook - the first cable was replaced, and when the second did not work, I suspected the logic board. After two trips to Apple, it still did not work. Monster cable was non responsive to requests for help. Finally, one of Apple's techs suggested I try the Apple cable, and he even sent me one n/c - and it worked. Dual usb/600/640ram Al vogel