Apologies if this is in the wrong place, I've experienced the same thing across other stackexchange sites but I spend most time here so I'm posting in meta here.
Browser is FireFox 22.0, with Ghostery, Adblock plus running but nothing on this site blocked.
Basically, when I open questions in new tabs, FireFox will freeze up whilst trying to load content on the new tab - usually waiting on stuff from cdn.sstatic.net and mathjax.org
I realise there's as much chance this is FF's fault as anyone's, I'd just be happy for it to behave itself by whatever means.