Ah, there's the rub. After using Ubuntu live to SBF the 621 file here
from 1KDS, I wiped cache and did factory reset. I then applied root using the ezCD method and the multi-device live-boot Linux CD, selecting to root the Droid X (with USB debug and non-market apps enabled). I wiped cache again, just to be safe. I installed the Droid X Bootstrap. But Bootstrap gave me a blank screen. I could select anything - backup/restore, flash zip file, reboot, wipe cache - when I hit the power button to execute, I got a blank screen and had to pull the battery.
For some reason, the Droid 2 root CD did not work for me - it got a kernel panic every time I tried it yesterday. I was able to load the 604 sbf, but that's not where I wanted to be.
BTW, the loop I was referring to above was not a boot loop, it was a setup loop. I was stuck setting up accounts, and it would not let me say "done setting up accounts." Can't figure that either. Anyway, stock SBF set that right.
After getting root, I was able to freeze a bunch of bloatware with Titanium Backup. I was able to boot to recovery. But once in Bootstrap recovery, I could go nowhere. I wonder of Bootstrap is flawed, because the rest of the system seemed okay. I had done full wipes, so the system should have been clean. Heck, I rooted over a system that didn't even have any user set up, I skipped setup and only turned on USB debug & allow non-market apps. Oh, and having the phone on 'charge only' did not work for me; I had to set it to PC mode. I'm running through the whole process again now. The one glitch in the process, at the very early stage of running the root says: rm failed for /data/preinstall_md5/magic md5/magic.md5. No such file or directory. (there's a letter missing at the beginning I can't make out, because it's off-screen). It doesn't do anything at that point, but then I reboot to bootloader, and it proceeds normally.
Thanks for looking at my post.