Check in your scripts in "Main" if there is something like:
unless $DEBUG
unless $keybd
$keybd = Win32API.new 'user32.dll', 'keybd_event', ['i', 'i', 'l', 'l'], 'v'
$keybd.call 0xA4, 0, 0, 0
$keybd.call 13, 0, 0, 0
$keybd.call 13, 0, 2, 0
$keybd.call 0xA4, 0, 2, 0
end
end
or something similar. Delete it. Now it should work always in window mode. You can switch between window and full-screen by holding ALT and pressing ENTER.