I don't use Adblock, due to its built-in list of "acceptable ads" (made of advertisers who paid for being white-listed...), but different forks depending on the profile used, so the bug is unlikely related to this add-on. All the more as I tried with and without these ad blockers, without any change.
I see in your list 3 or 4 add-ons I also use, antp, I'll make some tests. For the record, I already tested it: French language pack is not liable (I know that Australia and New Zealand have bad memories of French people due to the nuclear testings in the French Polynesia and to the Rainbow Warrior affair, so it could have been a very long-term revenge ).

By the way, shouldn't these posts be moved to a different thread ("Bug in the New South Wales plate tool when using Firefox"?), to keep this thread consistent?