While OS X may have the reputation of being a solid operating system, it isn't immune from occasional crashes and app freezes. If you've owned a Mac for a long period of time, you've most likely come across the spinning beach ball of death a time or two. Here's how to figure out which app is causing the problem, if you don't know already, and how to force quit the app:
That's all there is to it. The app you selected will shut down completely. You should now be able to re-open it again. If it keeps crashing, try to completely uninstall and reinstall the app as well.