Fullscreen doesn't work

I have problems applying fullscreen mode in STK 0.8 - see the image below:

link of the image: https://www.dropbox.com/s/lv0f2riih7bxo4b/tux.jpg
my Desktop-Resolution is 1920x1080 - on my old pc everything worked well but on a resolution of 1200x800 - but even if i change the current resolution into a lower one, it won't work...
can anybody help out? -THX

link of the image: https://www.dropbox.com/s/lv0f2riih7bxo4b/tux.jpg
my Desktop-Resolution is 1920x1080 - on my old pc everything worked well but on a resolution of 1200x800 - but even if i change the current resolution into a lower one, it won't work...

can anybody help out? -THX