Ahh, I installed it as a prerequisite to KUAL, but I did not register my Kindle at any point. It was suggested (
here and
here) that not being registered can cause the problem
I registered the device, and re-installed the "update_k4_ALL_devcerts_install.bin" file. After the update I did not get any error, nor after a restart following that. I also ran the chattr command, just for the fun of it. Thanks again for the help.