My Nexus 7 is stock. That is, no custom bootloaders, ROMs, clockworkmod, etc.
This morning I selected the notification to update to version 4.2.2 ota. I didn't pay attention to it for a few minutes after that, and the next thing I saw on the screen was a "dead" android with the word "error".
I held the power / vol- buttons until it restarted, but it wouldn't get past the flashing "x". I tried that a few more times, waiting up to 30 minutes, same result.
I figured out how to get to recovery mode, but since I don't have ADB installed and would rather not wipe the thing, I'm not sure what good that does me. (I have no idea what the clear cache option would do -- do I want to try that??)
Trying to do this:
http://productforums.google.com/forum/#!topic/mobile/ZSGv5zswdx8
http://support.google.com/nexus/bin/answer.py?hl=en&answer=2668668&topic=2840575&ctx=topic
Did nothing, except that now every time I go into recovery mode I end up with "no command".
I'm a noob -- I used to load CyanogenMod onto my Nooks using clockworkmod and a micro-SD card, but that's the extent of my "advanced" android experience. (I never could get ADB working with a nook, except through wireless.)
I got it working again. Through a very tangled combination of
Wug's Toolkit and
these instructions, I was able to wipe the device and reload 4.2.1. (Wug complained about the lack of ADB access and wouldn't complete the flash stock for me, but it was able to give me access to the bootloader through fastboot.)