A number of people have reported that while working in a planner that the planner can appear to hang or stop responding. While this can be caused by slow internet service it is most often caused by the web browser you are using on your computer system.
Web browsers store information on web activity in the browsers history or cache. It is a good idea to clear this cached information on a regular basis to keep your web browser operating at peak efficiency. For information on doing this please see http://www.wikihow.com/Clear-Your-Browser%27s-Cache