Where you able to access Facebook with another computer from the SAME location?
The padlock seems to indicate that Facebook is somewho locked out or blocked by a firewall or proxy.
Chances are that the network you are using to connect is configured to disallow access to Facebook, and quite probably some other sites, like Twitter and other social sites.
If you where able to connect with another computer from the same location, take a look at your "hosts" file.
Located in: C:\Windows\system32\drivers\etc\
Open it in notepad.
You'll probably find a line like this one:
127.0.0.1 www.facebook.com
Just remove it and save.
Electro
March 2012