1. Open your list of Add-ons.
2. Disable all but one or two of them.
3. Surf for a while (2+ hours).
Did the pop up reoccur?
NO = One of those disabled add-ons is causing the pop-up. Select another one or two to
enable. Repeat step 3.
YES = One of the add-ons that is running caused the pop-up. Select one and
disable it. Repeat step 3.
When you find the culprit, check the developers web site and see if there is an update to fix this behavior. If not ask him/them to fix it or tell you how to stop it.
Important! Please report back on their response and what add-on it is.
4. Enable FF to check for updates when it starts up (see your prefs screen). That should negate the need for any add-on to attempt any contact with its 'home'.
5. Take two aspirin and call us in the morning.