Disabled add-on then reenabled, and all the rules were gone
I have been using HTTPS Everywhere 3.4.5 for a few weeks with no dramas, but I found a site (librarything.com) that seemed to be broken (infinite redirect loop between HTTP and HTTPS) and even when I disabled the rule for that site it was still doing it. So I disabled the add-on, and tried again. It was still broken, so I re-enabled HTTPS Everywhere, and bonk! it was kaput-ish. :-(
No rules are listed anymore, and the submenu under Tools is empty (doesn't open when upon it I click).
Thanks for reading!