I was getting the "USB device not recognized" error when connecting my Zune. Resetting it with the left arrow and top part of the pad was not enough. I had to follow these instructions to restore the Zune:
http://support.microsoft.com/kb/927001/
The first few tries didn't reset it. But I eventually got it to reset. Once I connected it to PC with Zune software already installed, it worked like a champ again. So, not in all cases does a spare cord do the trick.
Your mileage may vary.
P.S. In attempting to determine what may have caused this, I realized that I had the Zune connected to my PC when rebooting the PC. I'll not do that again. But, at this point I"m not sure if that was a contributor.