Painter Essentials has stopped working

I installed Corel Painter Essentials 5 about a month ago and it worked fine. In the past few days it wouldn't start; I get the message "Painter Essentials has stopped working." I uninstalled it and reinstalled from a fresh download, entered my key, but it won't open (I get the first screen and then the error message). I need this product to work now; I will be teaching it to a Lifelong Learning group.