I have a similar problem that the site ceases to work with certain browsers.
I am pretty sure it's a combination of the stored profile (probably some cookie,) and the advertisements. It happens on other sites too.
My theory, at the moment, is that for my current profile the advertisement server either stalls or redirects to very slow sites, freezing the rendering process of PF web pages.
You might want to check whether you have the same problem by wiping all profiles/cookies under Firefox and see whether you can load the pages then. (I don't because I am too lazy to restore all passwords stored, so I usually switch browser.)