I found this thread earlier and copied it then. But now I can't locate it.
"Norton firewall is blocking parts of Facebook. It was working fine forever, then all of a sudden, Facebook will only load partial pages. When disable smart the firewall, it will load and work fine." (Edited for brevity)
I am having the exact same problem. It started a couple of weeks ago.
All other websites work fine. It is true for several browsers on more than one computer. It started three-or-so weeks ago.