Let me try to find a solution for you. I will get back to you.
First off, you can try to hold the alt-key when starting the game. A resolution dialog should pop up.
Otherwise hat you could try (while we try to get the grip on a more definite solution) is try to use the following command line arguments:
-screen-fullscreen Override the default full-screen state. This must be 0 or 1.
-screen-height Override the default screen height. This must be an integer from a supported resolution (e.g. 720).
-screen-width Override the default screen width. This must be an integer from a supported resolution (e.g. 1280).
So run it with -screen-fullscreen 0 -screen-height 720 -screen-width 1280
If you are not familiar with command line options, let me know.