You may be having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?
Whenever you have a problem with Firefox, whatever it is, you should make sure it's not coming from one of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode and select Disable all add-ons. If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and theme. You can troubleshoot plugins the same way.
If you want support for one of your add-ons, you'll need to contact its author.
i kinda have the same problem, whenever im using Firefox, if i close out Firefox, and then try to reopen a new page later, it wont open at all.. nothing happens, the little circle thing shows it loading but nothing ever happens. I prefer to use Firefox, but i cant if i have to restart every time i need to open a new page, or if it wont work with pop up windows for like games or some websites that use pop up pages to confirm.. even turning off pop up blocker doesn't work.. ugh so aggravating.
I have the same problem. I updated my Motherboard audio drivers, afterwards Firefox would not open. It shows in Task Manager, but that's it. I have tried uninstalling and cleaning all folders, tried different versions, turned off virus scanners, scanned registry, checked hosts file, tried Seamonkey., nothing has gotten Firefox to open. Chrome, Explorer and Opera work, but nothing Mozilla related will open. I can't even open Firefox in safe mode. I've also tried to change the read-only settings in %AppData%, but that didn't work either.
I did the same thing on my other computer and had to wait a month before I did something(I have no idea what) and Firefox would work on that PC. I'm going nutz trying to figure this out. I have searched all of Mozilla support, but still no joy.
I'm running Win 7 if thats helps diagnose anything.
right click on the toolbar on your desktop. click "task manager" or "start the task manager". then click on processes. click on anything that says something like "firefox.exe" or something like that, then click end procces. do this for every "firefox.exe" that you see. then start firefox. your problem should be resolved.
Disabling a Skype extension did it fixed the issue with me. Now Firefox will properly close. If you have downloaded skype it is most likely that you also have the extension and it may be causing problems. Go into your add-ons menu and disable it. Otherwise it may be another add-on that is keeping your firefox from shutting down properly