This happened to me and a co-worker too, and I could resolve it with a `sudo killall firefox` and re-starting it.

In contrast to all the heat from many of the comments here, I'll say this: shit happens to any company. My trust in Mozilla is not (yet) shaken just because a bug made it into production, even if that bug made it there due to bad decisions or even (hopefully temporary) lack of vision.

I, for one, am not comfortable with giving full control of the internet to Google and friends, so using FF is one of the things that let me "fight".