I was finally able to update the firmware on my device. Found that I had a completely seperate problem... that I thought I had a ZV:W when I actually had a ZV!
Once I tried the correct firmware, it worked immediately. I feel like an idiot. :-/
On a related note, I did buy a ZV:W because I had bought a hard drive upgrade that was not compatible with the ZV. Found one on eBay that was 'status unknown' and took a chance on it. Charged it up and it seems to work fine. I will have to replace the battery because it has outgassed and expanded, but for now it's working fine with the AC adapter alone. I did my HDD upgrade (using a Toshiba MK1231GAL -- 120MB 5mm thick drive) and it seems to work. The first time I tried to load the firmware I got a message that it failed. The second time I tried I also got a message that it failed, and I rebooted the ZV:W and got a 'firmware problem' error. Tried a third time... and got called away for a while. Message on my PC said the firmware load failed, but the ZV:W was up and running just fine. I think it was because the drive format hadn't completed even though the recovery menu returned from the format almost immediately... only thing I can figure. Anyway, I'm going to give it a go and see what happens and I'll report back after a few weeks with it.