I have a strange problem on Windows Vista (Automatic updates).
Long time ago I had installed Firefox, Thunderbird, Safari and Opera and they all worked well.
Once upon a time, after Windows restart, Firefox, Thunderbird and Safari won't start. [Opera (USB) works fine].
When I start the browser, program name is listed on the processes list, but it is not activated, doesn't show any window.
I tried crating new profiles with
-ProfileManager, restarting Windows, reinstalling the browsers. I scanned the system for suspected programs and it looks clean. There is 45GB of free HDD space.