Wow, i had this issue again so I can back to see how I solved it the first time, not knowing so much conversation had happened since! Anyway, for me, I have learnt to check the registry AND the settings.cfg, resetting both to get over the issue. I used to always run windowed mode, but I tried switching it to fullscreen and back, somehow I couldn't, so I went into the settings.cfg to do it manually. When that was done, although it was "windowed", but there was only the picture, no actual window frame was visible, and I couldn't figure out why...