I'm a newbie to Bela, but had Beaglebones for a while.
I can get 0.3.6b to boot on my Beaglebone Enhanced (blue) off SD, but not my original BB Black.
BB Black boots my other SD card images OK with user button held down.
Only critical difference I can see is that the BBBlack has the original "BeagleBoard.org BeagleBone Debian Image 2014-04-23" image on it. Is this likely to be creating the pain?