Don't forget that this isn't the only method of debricking. It certainly is the most powerful one, but for "simple" brick cases, (i.e. when the Kindle still appears as a USB drive), the data.tar.gz method could still work. Give it a try, you have nothing to lose:
1. Plug the Kindle to your computer. If it shows up as a usb drive, put both files from here
on that drive, then eject it.
2. Reset the Kindle (press power for ~20 secs, until it restarts)
3. The jailbreak will be installed, at the same time trying a factory reset. This sometimes hangs after execution, so if you see the jailbreak screen for, say, 2 minutes, just reset it again.
No guarantees, but I know this method has worked for at least 3 people whose Kindle was stuck in the same state as yours.