Firefox Firefox Wont Start But When I Open A Link That Opens Firefox, It Works Fine. What Do I Do?

Firefox wont start but when I open a link that opens firefox, It works fine. What do I do? - firefox

Every time I Firefox, it crashes immediately. I tried to open it in safe mode and still does not work. I even tried to change my homepage. When my friends me on my MSN Messenger, open Firefox link and it works well, I can surf the Internet as usual. What should I do? I uninstalled and reinstalled.