Thanks Zear, I edited the chocolate_strife.cfg file, and it seems like fullscreen was enabled (set to 1). I disabled it, and made sure it was also disabled in chocolate setup and now it works.
Also, I've really been enjoying UMG, can't wait for it to be finished. The controls are very polished, definitely my favourite homebrew game in a long time.
Sounds good Johnny, thanks a lot for your efforts as well!