I got this cable trying to sync the new iPhone 3G, but kept getting an unknown 0xe8000001 error. I tried a bunch of things and was using the combo Bluetooth headset charger plus USB connector. On a lark, I swapped cables and the error 0xe8000001 went away. I think the cable was flaky. I did notice that when I pushed in harder, the iPhone 3G would actually connect.
So next time this happens, it might be the cable. Makes sense to me this particular cable has been everywhere traveling in my bag.