Collapsible fieldsets' titles vanish on Firefox 2.0.0.1.

The title for a collapsible fieldset doesn't always render. This bug is small, sneaky, on the rare side, and browser specific.

On Firefox 2.0, if a collapsible fieldset is expanded by default (#collapsed=FALSE), the fieldset's title and its collapsibility arrow don't always render when the page loads. As a result, it's not possible to collapse the fieldset.

There are several things that prevent the bug from manifesting, or that might keep someone from noticing it:

• It's specific to Firefox 2.0: I tested multiple page loads on each of IE7, IE6, and Firefox 1.5, and the problem never occurred once.
• It never happens to a collapsed fieldset.
• It doesn't happen on every load of an affected page. Sometimes it seems the position of the mouse cursor affects whether the bug appears.
• Expanding a #collapsed=TRUE fieldset will make the make the missing title reappear on the first expanded fieldset that follows it on the page. Second and subsequent following fieldsets are not affected, and neither are any that precede the triggering fieldset.
• Right clicking on a menu link will fix all fieldsets that come after it on the page. It doesn't work for any other other kind of link that I can tell.
• If either the SimpleMenu menubar or a DHTML Menu block is enabled, all fieldsets work correctly.

For all I know, the JavaScript in question is all perfect, and this is entirely a Firefox problem. On the other hand, some poor slob is going to end up pulling his hair out either way, so perhaps it would be worth building in a workaround.

If it matters, all the browsers I tested with are on Windows XP Home SP2 or Windows XP Pro SP2. I tested against two servers running Drupal 5-rc2, and also against CVS updated at 10:30 on Sunday Jan 14. (That's form.inc 1.174, and collapse.js 1.9.). Both servers are running XAMPP 1.5.5, with Apache 2.2.2, MySQL 5.0.27-community-nt, and PHP 5.2.0. All sites were configured with mysqli and Garland.