Firefox crashes on startup after upgrade from 3.6 to 11.x (I think it also crashed when I tried upgrading to 10.x when that was the latest). Also crashes in safe mode, so I guess the plugins don't matter? Also crashes running firefox.exe -p Doesn't create a crash report. No error message and no window appears before the crash. Just the windows message saying it crashed. Still crashes after a clean install. Works fine after I reinstall 3.6 back in. OS is Vista. I don't have any of the programs like roboform on that list of programs known to cause issues.
Re: Firefox crashes on stratup after upgrade to 11.x
There is a possibility it is hanging rather than crashing, look for any instance of the process firefox.exe or plugincontainer.exe that is still running and kill them before checking again.
Safe mode does not prevent plugins running. You will need to disable them, or in some cases uninstall them. Starting in Windows own safe mode by using the F8 key could help. There is also the possibility it is a malware problem.
The standard troubleshooting step is to create a new profile, but you are having problems with that. There is a standalone Profile manager you could try.
I think you will need to start with a clean reinstall, but before you do that copy your existing profile; including sub folders and files; somewhere safe outside the Firefox program and profile paths (such as onto the Vista Desktop). Then delete the Firefox program folder or uninstall using Windows control panel. Before proceeding to reinstall restart the computer and check the program files have not been restored by any security or backup applications.