That's due to security keys in Linux kernel v.3.4 which necessitates a new bootloader service inside the BIOS (aka the bootloader), which then load the security keys first to ensure the kernel is valid before loading. Older kernels will obviously fail as the newly-updated BIOS would think that the kernel keys are invalid, thus automatically halting the boot procedure.
(EDITED) To be able to put back in your favorite Jelly Beans distro, you must downgrade the BIOS (bootloader) BUT DO NOT downgrade the Trustzone (*.tz) file or you will do great job of bricking it for good. There's also KK to JB downgrade thread which you can follow the instructions to do so.
(Mod: you can choose to delete or move it to proper thread - just elaborating on the bootloader's boot procedure.)
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Last edited by Dr. Mario; 7th July 2014 at 12:29 AM.