NOTE: The reason you see "sudo" before all of my commands is because I'm running Linux.
OK, so I somehow managed to bork my tablet, then got it back up and running using a deodexed boot image someone posted up on here... but then I realized it was a 4.1 boot image, and could not get it to update to 4.1.1. Sooooo I decided to go back to stock.
Following the directions in the OP, I got to this step:
And I get this error:
sudo fastboot -w update nakasi-jrn84d/image-nakasi-jrn84d.zip
archive does not contain 'boot.sig'<br />
archive does not contain 'recovery.sig'<br />
archive does not contain 'system.sig'<br />
< waiting for device >
Doing a "fastboot devices" showed my tablet. I just could not flash the .zip file. After I got done cleaning the fudgie out of my pants, I tried unzipping the zip file and individually flashing each image file:
sudo fastboot flash recovery recovery.img<br />
sudo fastboot flash boot boot.img<br />
sudo fastboot flash system system.img<br />
sudo fastboot flash userdata userdata.img
All of these worked. I rebooted back into the bootloader, then started my device up, and everything appears to be good.
Just wanted to pass this along in case anyone runs into the same problem.