So When I Run The Demo It Starts And When I Click Sandbox Its Crashes And Shows This Dialog. I Had It Running Perfectly Before And Now It Started Doing This.
It shouldn't, but to be safe I would move the Platforms, Models and Engines folders (Documents/Automation) somewhere safe so you can return your saved cars if they were to be deleted.
Thing is, it is probably your models / platforms causing the crash. Before redownloading / installing, try to move the respective folders away and see if it works.