I have 3 Zune 30GB running within my house. None of them having issues that you guys have been stating. I was actually expecting them to have the issues that you guys are listing because they are v1 Zunes.
The firmware issue does indeed seem to be some sort of firmware error. It's entirely possible that it could be from the update. That's the ONLY time those files are modified. I know this may sound like a curse, but call Zune Support. They may be able to give you a better explanation. Also, make a note of any sounds that may be emitting from the unit itself. If there are any audible clicking sounds, then the unit might need to be sent in.
As for the poster about the size limit, you will probably have to reformat your Zune. Changing PCs often to sync your Zune can affect the meter on the Zune software. Im not entirely sure if this would also affect the unit itself, but I have a feeling that a simple reformat might fix the issue.
Proud owner of a Zune HD 32GB
Halo 3 30GB
2 Zune v1 30GB