So, turns out I'm in a bit of a similar situation.
The OTA update went through and downloaded and I wasn't paying attention because I thought I had blocked them. Apparently not and I was an idiot and told it to reboot as I was finishing tweaking swiftkey X.
Now I'm stuck in a loop. The update reboots the phone, Clockworkmod Recovery loads, fails to verify whole-file signature, and stops. Next when I restart the phone again it goes all the way into android, waits a few seconds, then says "Shutting down" and tries to apply the update again! I have airplane mode enabled and the same thing occurs.
I do have the phone in USB debugging and Charge only mode, so I'm thinking about trying to unroot the phone to return it to stick (and thus wipe-out the update file, wherever it is) and then making the decision on if I want to re-root or stick around until GB comes out for real.
Is this a reasonable path to take? Or is their an easier way to just strip out the update file and unflag whatever is causing the reboot? I'm just running the standard rooted rom, not GB or anything special. The only thing I've done is get rid of the bloatware and install wifi tether.
edit: Doh. booting into Hboot and reflashing the pg05img.zip still on my sd card from the original root seems to have solved the problem. Of course now I have to set everything back up again but that's still preferable to a useless phone!