If you are on the US or EU versions of JFv1.51, you'll likely get an OTA update notification soon, if you haven't already. I had accidentally left in the otacerts.zip file, which allows OTAs to be downloaded and verified.
For now, there are a few possible work arounds.
1. delete the otacerts.zip file manually. The file is at /system/etc/security/otacerts.zip But keep in mind if you use this method your phone will continuously re-down the OTA and try to verify it, which is bad on your bandwidth usage and your battery life
2. Replace /system/build.prop on your phone with the one from the ADP1 version of JFv1.51
3. chmod 000 the OTA file in /cache (unconfirmed solution, but is likely to work)
Or you can ignore the popups for now, and wait for my new release based on the new update (CRC1). I promise to "disable" the OTA mechanisms in a better way than simply deleting otacerts.zip :). I should be able to get something out soon (next few days)
In the meantime, even if you accidentally hit "accept" on the popup, it won't be able to install the update when it gets into recovery, so you aren't at risk of losing root access.