Hello sabman! Glad to know I'm not alone. Come to think of it, I think it did start when I manually chose the Hibernation Mode (which, after reading these forums after the fact, I now realize was a bad choice.

As far as getting the update to work, I tried many, many times and failed. Here's some tips to help (I've included everything, just so that these instructions are complete for anyone else who lands on this thread):
1. The update.zip file must be exactly named "update.zip"
2. The update.zip file must be located in the root folder of the USB drive (i.e. when you connect your USB drive to your computer, and it's assigned the drive letter F:, then the file must be in F:\update.zip. You cannot place it in a sub-folder on the USB drive). I don't believe that having other files/folders will matter (it shouldn't)- but if all else is failing, it doesn't hurt to try getting rid of all but the "update.zip" file.
3. **Use a USB drive that is 2GB or less in capacity**. The reason I emphasize this is because this was my issue. As an IT professional, this advice holds true for most computing devices. When it comes to boot-loaders, firmware recoveries, etc., most devices cannot properly recognize or access drives larger than this. Now, newer devices are increasingly overcoming this limitation, but so far I've found this to be true for even the newest of devices.
4. Make sure your device is off! Remember, there are sleep and hibernation modes on this device- just like a computer. You need to be sure it's off-off (pushing the reset button seems to always get it to this state) so that you can "cold boot" (as they say in the computer world) as opposed to a warm boot (which is what happens on your computer when you choose "Restart" and the computer automatically reboots and starts up without having to press the power button).


Sabman- You are correct that the I cannot confirm that I have successfully downgraded (because I get the white screen from the second I turn it on)- but the facts that I used to all but confirm it are:
1. The boot process takes much longer than usual
2. The light on the USB drive indicates that it's being accessed multiple times during the boot (it will flash for a little bit on a normal boot up- the key is if you see it get accessed for about 10 seconds, 2-3 times in a row with a long pause between)
3. The ereader changes to "Initializing" and stays there for the entire boot process (if it changes to the menu with the "Read, Write,..." options then it booted into Android and did not enter the recovery mode)
4. After several minutes of reloading the software, the device "reboots" (The LCD goes black, then comes back on and the speakers "pop", which is usually a sign that the device has powered off and then back on).
5. After it boots up, the ereader requests a calibration- exactly as it did from the factory.
6. After the LCD shuts off, pressing a button wakes it up but if you don't unlock it, it goes to sleep again within seconds (as it should). However, if you press the menu button while it's awake, it "unlocks" and the screen stays awake for the appropriate amount of time (can't remember what the default amount of time is, but it's 1-3 minutes I think). If you recall, Ermine employs the "slider lock" and if you attempt to slide the lock on the screen to unlock it, it doesn't work (which I was able to do repeatedly and reliably after getting the white screen under Ermine).

So, not a slam dunk- but from my observations I can reasonably assume that I've successfully downgraded to Dingo.

One other note- in my case, if I look at the LCD screen from an extreme off-angle (i.e. looking at the screen from nearly the side edge of the device), I can see faint shadows of menus of the screen. Now, they don't necessarily correspond to the actual menus and you cannot make out anything from them (nothing is readable), but I was able to confirm that the touch screen is still operational. Going off of memory, I can touch on the screen where I remember an icon being and it will perform the action.