Definitely sounds like a device issue, it could be that the hard drive is starting to fail on your Zune80. :( This error happens when the software tries to to send data to the device, but the device does not accept it, for whatever reason.
My only suggestion is to disconnect/reconnect the device, and/or reboot, but it sounds like you are doing that already.
Matt Akers
Zune Product Team
.: This posting is provided "as-is" with no warranties, and confers no rights :.