How To: Fix Zune "Device Cannot Start" Error | Posted at 3:10 PM
This problem, for me, was caused by using a USB hub connected to my computer. This did not provide enough power for the Zune so Windows notified me that the device could not start.
To fix it, simply plug the USB cable from the Zune directly into the back of your computer's USB ports as those should have enough power.
That worked for me.
(I am running Windows 7 64-bit (x64))