Well, I turned on my machine this evening, and I wasn't able to connect to the internet. I double-checked everything, and it all appeared normal.

Who knows, it might not be Mozilla's fault, but all I know is that most of the settings on Firefox had been reset (homepage, security dialog boxes, etc), and when I finally did connect to the internet (without actually changing anything), I was taken to Mozilla's site with a message that the preview build of Firefox has been released. This is good news, but I hope it's not what caused me so much frustration for a couple hours.