[Barnes & Noble Nook Tablet] kring789:
I busted my Nook Tablet, tried a hundred different things to fix it, and was about to give up, when I finally found the solution. This is my story.

Seriously, though, this forum has been a huge help to me, and I'm posting this in the hope that it will help someone.

First, a little background on me. I'm a software developer, and I've even contributed a bit to the development of the gingerbread-based CM7 for the Droid X. So I know a bit about Android, but I don't pretend to understand everything, especially on the Nook Tablet. That will become clear as you read the rest of this because I can't really explain some of the things I experienced.

Using several of the helpful guides here, I successfully booted ClockwordMod Recovery off an SD card, rooted my tablet, and installed the CM7 alpha (http://xdaforums.com/showthread.php?t=1481826). Since booting CWM off the SD worked so well, I didn't feel the need to install it internally. It was a beautiful thing.

By the way, in order to boot CWM from an SD card your tablet must be plugged into USB! At least that has been my experience, and it hasn't always been made 100% clear.

Then, I bought a new SD card - the one I used originally was borrowed from another device. The new one was 16 gig. I wanted to make sure I could still use it to boot into CWM, so I started out as before by writing the image found at

http://xdaforums.com/showthread.php?t=1488035 to my SD card using Win32DiskImager.exe, which I acquired from http://xdaforums.com/showpost.php?p=21895025&postcount=14. But this repartitioned my 16 gig SD card down to 2 gig, so I used gparted in a Ubuntu VM to resize the partition to 16 gig.

I had all sorts of trouble getting into CWM with this new SD card. I don't really know why. Maybe the partition resizing was an issue, I'm not sure. But after lots of attempts, including plenty of failed boots, I started getting the dreaded black screen saying, "Please restart your device and try again. If you encounter the same issue, please contact customer service or visit: nook.com/tablet/support." I couldn't boot up CM7 anymore.

At this point I switched back to my previous SD card, plugged in the USB cable, and was thankfully able to boot into CWM. I tried the usually stuff. Reset data. Reinstalled CM7. Restored the backup of the factory ROM before I installed CM7. Nothing worked, I always got the "please restart" screen. Then I tried the 8 failed boots method to restore the factory state. It wouldn't go into the restore mode, just the same garbage again. At this point I figured I had really and truly bricked my device. This thread (http://xdaforums.com/showthread.php?t=1397262) describing a similar problem didn't give my any confidence.

But since I could get into CWM, I realized I should at least be able to get into a shell via ADB and have a look around. Getting ADB working was a challenge, but eventually this post (http://xdaforums.com/showthread.php?t=1363652), installing the USB driver attached to this one (http://xdaforums.com/showthread.php?t=1354487), and adding the necessary line to adb_usb.ini (see the runmefirst.bat in the previous link) got me up and running with an adb shell.

I suspected my problem had something to do with triggering factory reset mode with so many failed boots, and somehow that factory reset mode was broken. With that in mind, I eventually stumbled upon this post (http://xdaforums.com/showthread.php?t=1444630). I use CWM to mount /bootdata, logged in from my computer with "adb shell", and issued the dd commands the post described to reset the BootCnt and BCB files. I had to remount the bootdata partition read/write with "mount -o rw,remount /bootdata". If you do this once and still get a "Read-only file system" error when you do the dd command, just try the mount command again. I don't pretend to totally understand why that would be necessary, but it seemed to be necessary for me.

The first time I tried this and rebooted, I still got the same "Please restart your device error." It took me a couple of tries to figure out that I had to issue these commands and then remove the SD card before rebooting. It seemed as if booting from the SD card somehow re-poisoned the device so that even once I removed it I was still in a bad state.

Once I did this my device booted back into CM7. I shut it down, used the 8 failed boots method, and was able to reset to factory successfully. So apparently I was in some sort of badd BootCnt/BCB state, but it wasn't just the regular 8 failed boots state. I'd love to hear an explanation of why this might be, if anyone knows.

TL;DR: if you get a "Please restart your device and try again" error and nothing seems to fix it, try this:

1. Boot into CWM off an SD card

2. Mount /bootdata via CWM

3. Log in from your computer using "adb shell"

4. mount -o rw,remount /bootdata

5. dd if=/dev/zero of=/bootdata/BootCnt bs=1 count=4

6. dd if=/dev/zero of=/bootdata/BCB bs=1 count=1088

7. Remove SD card

8. Reboot