As some of you who have rooted your Kindle in the past, have recently had an issue when 6.3 is applied.
If you have rooted your Kindle the update breaks your Kindle Fire in a strange way.
For me, it would power off then reboot to a little Android robot with an exclamation point.
Well there are many updates out there to Root your Kindle running the 6.3 software, but the easiest I have found is the following images from this post:
Thanks to eldarerathis.
You simply download the image and apply the ROM and your Kindle Fire will be rooted again, until the next Kindle Fire Update.