Hey guys,
Just won a Zune 30GB Halo 3 Edition, and couldn't get it to work. Tried everything, unistalled Zune, uninstalled drivers, disconnected, reconnected, rebooted my laptop, rebooted the Zune itself, nothing worked for more than a few seconds. I read a post above that recommended unistalling LibUSB. Well, I tried it and everything is working fine now. For vista users, here's an easy way to do it.
Open start menu
Type "libusb" into the little search bar at the bottom
"Uninstall LibUSB-Win32" should appear at the top. Click it and click next to uninstall.
Worked like a charm for me.