Collapsible fieldsets break with latest dev version

I just updated a 6.x site's modules yesterday using Drush. It got the 6.x-2.x-dev package for jQuery update. After the update, both draggable tables (already addressed in a separate open issue) and collapsible fieldsets were broken. Basically, they end up open or collapsed correctly depending on their default state, but cannot be toggled (clicking on them does nothing). I had to disable the module to get them working again. I know next to nothing about jQuery, so I really have no idea how to debug it.