Are you using App Designer with App Framework? There is a bug with App Framework which brings up the github page and XDK cannot be closed after that. Please force quit the XDK and use other framework Bootstrap or Framework 7 or Ionic. App Framework has been deprecated.
@lucianopalma, I understand your frustration. To give you a better picture, the above annoying bug is being fixed and the fix will be available in the next release. With that, for now you will be able to use App Framework with App Designer, however in future releases of XDK we will remove App Framework from the App Designer. Having said that you will still be able to use App Framework independently, you would have to include it manually in your project from https://github.com/01org/appframework. ;The App Framework project has been open sourced and Intel is not putting extra resources to maintain/update and hence it's deprecated from the XDK IDE, but you are welcome to use it in the state it is now and with the updates from the community.