When I launch Firefox 44.0, it opens, but as soon as I try to do anything (even pull down the bookmarks menu), it hangs. If I go to the Force Quit box, that shows Firefox as "not responding", and I can quit Firefox by clicking on that entry. Because the program hangs immediately after launching, I cannot even begin to work through the troubleshooting menu. The program was working well until a week or so ago, and then began slowing down markedly. I have tried re-installing from the mozilla.org website several times, but it doesn't work. I suspect that some malware has taken over my computer, but I don't know where to start to deal with it. My computer is a MacBook Pro, and the operating system is Lion (10.7.5). Because Firefox isn't working, I'm using Safari now, which works fine, but I would like to get back to using Firefox.