You CAN brick the droid x. Try updating to official 2.2 then flashing sbf back to 2.1. See what happens
I actually just did that....had official 2.2 on my phone....somehow got out of sync by installing the clockwork recovery (I think) and got stuck at the M screen forever....eventually sbf back to 2.1....then re-root...then reinstall droid x bootstrap from market...reboot recovery....restored nandroid backup...all is well.