Go to options and change to Windowed mode, and it won't go into Windowed mode.
Expected Results: Fixing the issue to re-allow windowed mode.In order to change from full screen to windowed you have to...
1. Go to Options
2. Change to Windowed mode
3. Change the resolution (1920x1080 isn't currently in the windowed resolution list)
4. Apply changes.
Note: I am able to change to windowed from full screen for any of the resolutions that are supported in windowed mode.
This is a known issue, there is a work around to get it to function. When changing from full screen to windowed you then need to change to a different resolution. This should allow you to change into windowed mode.