My work recently provided me with OSX Mountain Lion to use while telecommuting. In the office wireless worked great but when I got home to my home office I was unable to login to any site that required SSL. These are the sites that start with https:// up in the URL bar. Digging around on the internet I found that this is not an uncommon problem.
Apparently, my little Belkin router cannot handle OS X’s default 1500 Maximum Transmission Unit (MTU) setting. By altering it to 1453, a number referenced at OSX Daily, the sites once again worked.
The quick fix:
System Preferences > Network > Advanced > Hardware > MTU: Custom -> 1453