The Zune Pad on my 80GB Zune was unresponsive for a day or so and a normal reset or restore didn’t work because they require the Zune pad to be working.
This worked for me, give it a try:
Plug Zune in computer via USB
Go to the Zune Software
Click Player Update
Click Install Games (button)
The software will be installed and when the device reboots it should be functioning.