toggle all the events off and try again, if it doesnt change then the problem isn't in your event sheets. Also disable any effects you have in your layers/layout.
That pretty much will narrow it down to either the project settings/ configuration settings in construct or the build settings in the xdk.
try switching to the fullscreen in browser to letterbox if it isn't already.
make sure the 'first layout' setting isn't a blank layout
Beyond that I will probably need to see the .capx