Try resetting your device completely (clearing all firmware and content) by following the instructions on
this page. If you own an older Zune device (30/4/8/16/80/120), look under the header that says "
Formatting and reinitializing your Zune30/4/8/16/80/120 Devices", and use the Initialize Disk method for whichever device you own.
Hope that gets it working again so you can re-install the firmware!
Corey Shuster
2009 Microsoft Zune MVP
My responses come only from personal experience.