Hmm, my Firefox automatically updated last night as well, and it's working just fine. However, in my Internet and Web Design class at school, I downloaded and installed both Firefox and Opera to test for browser compatibility and Firefox does not detect the Internet at all (no matter how much I change the settings), while Opera and IE work just fine.
I would suggest checking the
Firefox Help and Support Page, to see if they have anything useful information that might help you to solve this problem.