WordPress 4.0 causes firefox loading circle to constantly spin

Hi all,

I have two domains running with WP 4.0 and with both of them the loading circle (the blue circle in the tab next to the site title) in FireFox never stops spinning. This occurs on both back- and frontend on both domains. The pages are loaded just fine, it just seems that the browser is waiting for something even though the page has loaded and looks fine.

domain 1: webanalyticsprotips.com
domain 2: billigtforbrugslaan.dk

For domain 1 it started when I updated to version 4.0. For domain 2 it was a clean install of version 4.0 and it did it from the beginning, which rules out it is caused by a plugin or the template.

I viewed the domains using Safari and Chrome, but I only see the issue on Firefox (running version 32.0.3).

Any ideas to what is causing it and anything I can do to fix it? Despite not causing any bad experience it is slowly driving me crazy. I re-installed wordpress on domain 2, but it even did it on a clean install.

Thanks,
Kasper