[I posted this earlier this morning but I put it in the wrong sub-forum. Someone was trying to clean that up and move it and it accidentally got destroyed. I'm re-creating it. I don't know if the other posts that were in it will be salvaged or not, but here's the OP.]
I got brought in on this by someone who hit my Gtalk on my phone at 4:30a to let me know that the world was coming to an end -- more or less.
In the last couple hours we've sorted out a lot and the deal is, in the new Droid X OTA it appears that they have replaced the entire HAB chain from the mbmloader (the loader for the boot loader) on forward. The keys that were used to sign the prior HAB components are no longer trusted by the new HAB components. What that means is that if you take the current OTA, and then subsequently use an SBF (or any other method) to replace a signed code group (which is just about every code group on a DX) that signature will not be valid and the boot process will halt when that CG is encountered. Since pretty much every SBF contains the "boot" and "recovery" code group, as well as the very-critical "CDT" code group, this means if you apply an SBF to your OTA'd phone (that is now running the 30.03 bootloader) your phone is toast. But not permanently.
In the above scenario you will still be running the new mbmloader (GC63) and mbm (CG30), so as long as you put code groups back on that are signed with the new signatures, you'll be back in business. None of the prior SBF's are going to help you -- they are invalid as of this OTA.
I'm sure Verizon is expecting this and has the 2.3.13 SBF standing by in the retail stores so they can flash you back to stock and get you working again (and give you the evil eye when you lie about how your phone got this way -- because I'm sure they have been warned about this happening in advance).
That's all for now. Hopefully this helps avoid too much unnecessary confusion, so you can just concentrate on dealing with the necessary confusion.
Oh, and to all the people who mocked when the idea of a hostile bootloader via OTA came up in the Droid 1 topic, well...