The list of images to be blocked by Adblock, as well as all other preferences and settings, are located in your user profile, so deleting it and reinstalling Firefox resets everything the way it was upon the first installation. Are you sure you closed and uninstalled Firefox, then deleted the Firefox installation folder (local drive:\program files\Firefox) and the profile directory (local drive:\documents and settings\username\application data\mozilla\firefox\profiles)? Try doing it again, in that order...there's no reason that shouldn't work. If, for some reason, they are still blocked you'll probably have to disable AdBlock whenever you visit the ite(s) that display those images.
Hope this helps,