Several web-pages can't be scrolled

Currently, when I go to the dashboard, there is no scroll-bar, and using a mouse's scroll-wheel has no effect. If there is a long newsfeed, I can see nothing beyond the bottom of the browser window.

This is also the case for issue-pages (more critical, since comments below bottom of screen can't be seen), and repository overview pages (can't see all of the README file for a repo). Probably other pages are affected as well.

(Using Firefox 16.0.1)