From my efforts, I find two CD's are necessary for solving any
issue with the DX - SBF to a completely original state
, and the root CD described at the top of this thread. Reset/wipe, root, fail, crash, SBF, reset/wipe, root. I've run through that sequence at least three times (and I hope I've got to a stable point, assuming I don't muck things up again). If you can get to the boot loader, you can restore this phone.