Firefox is being weird. Once it opens, it's fine, of course. It's the opening it up part which is not bloody working.
As I whinged recently, every time (then it was sometimes, now it is every time) I open Firefox it asks me "which account do you want to use to run this program?" Uh, THE ONE I AM LOGGED IN TO, NUMBNUTS! I say okay to the dialogue. And more often than not, Firefox doesn't start.
The first time this happened, I opened Firefox again and again and again, and finally decided to use Safari for Windows. I like Safari, I use it on my Mac, but the Windows version is a wee bit buggy; I prefer Firefox on Windows. I'll make do with Safari (the other option is far less pleasant in my vIEw) but would like for my Firefox to, I don't know, work?
So the next time it happened (after my start-up) I tried to open Firefox three times after the dialogue (to no avail) and then I three-finger-saluted my way in to the Task Manager. There, lo and behold, there were several Firefox "tasks" running. Of course, I had to end each separately (why a single program can be opened multiple times is a quirk I will never understand), and once I did, tah-dah!, Firefox started up.
So that's my daily routine, now. Start Firefox. Say yes to the dialogue. Start it again, go in to task manager, kill the Firefox tasks, and then, actually launch Firefox.
I. Hate. Windows.