Running Firefox 19 and Vista/Windows 7. My computer got one of those "critical Windows updates" and installed automatically. Afterwards it would not run Firefox. Firefox did not crash--it simply never started running in the first place. The most information I could get was that Firefox was now incompatible. Malwarebytes was able to connect to the internet, but not my browser. I did a system restore to before the update and it all works for now, but that's only a temporary fix. Any ideas would be welcome.