Motorola Droid X :: Lost Root After 2.2 / Revert To 2.1

Go into recovery (like you did to apply the update.zip). Wipe your cache. Perform a factory reset/date wipe or whatever it's called from within recovery. You _should_ (again I take no responsibility here) boot into 2.1 where you can root and then apply 2.2 update again. Good luck, and let us know if it does/doesn't work.

To revert to 2.1:
1: Flash sbf. After this, you will bootloop.
2: Get into recovery like you did when you updated to 2.2.
3: Wipe cache.
4. Factory reset.

When you reboot you should be at stock 2.1. This would be useful if you needed to return the phone for warranty services, or if you need to reinstall 2.2 for some reason (like to gain root).