AT&T to JME boot/recovery fix
Sorry if this was already posted but I banged my head on the wall for a while before I figured a fix so may be it will be helpful to someone.
I tried to flash Roto-JME over brand new AT&T Tab. All went smooth but at boot up I saw AT&T start screen followed by black screen with vertical white line on the right. Then device would boot ok. I would get the same screen in recovery mode.
I also tried to flash JM6 but result was the same.
I figured that it must be something with SBL/PBL from AT&T not liking European Tab kernel (or other parts of firmware).
Long story short - I flashed JJ4 because it contains boot.bin and sbl.bin and they are not from infamous JMA/C/D etc signed firmwares. And voila - now I have regular Samsung logo and normal boot without lame white line.
After that I flashed JME and had no problem since.
The end result - my bootloaders are not signed:
SGT-BootloaderCheck v1.0 - Copyright (C) 2010 Chainfire
zImage: SIGNED !
-- Bootloaders: Unprotected, can flash all bootloaders and kernels
-- Kernel: Signed, can be flashed on all bootloaders