It works for mine, I tried Chrome IE9 and Firefox. (in preview)
I have a beta online for testing here:
does f11 work for you with it?
it's in letterbox scale mode, webGL on, hide address bar=no
do you have functions to scale the screen, or do you let Constuct2's scale do it? I had to remove all my manual scaling, it seemed to conflict. (the background wouldn't always scale until I took my scaling out.)
Ashley will probably need a Capx example, can you make a new almost empty Capx that also won't go full screen?