Description

If you have problems with collapsible fieldsets staying permanently collapsed because you cannot click on their titles (because the titles do not show), I frankly have no idea what the odds are that your problem is the same as mine.

But here is what my problem was:

My theme had an opening strong tag with no corresponding closing element (dynamically inserted into page.tpl.php from template.php to somewhat semantically style the site name). Firefox responded to this by throwing opening and closing strong tags all over the document, actually adding them to the HTML.

So, yeah, fixing the broken HTML fixed the broken javascript fieldsets. I didn't say it was an exciting story...