Unreal 1 help

[GolemsVoice]

I recently acquired the Unreal Anthology (back to the roots, baby) and started playing Unreal 1 right away. For quite a time, everything was alright. But recently, everytime I load the game, my screen is "framed", with one "frame" being added everytime I load.
http://www.imgbox.de/?img=l51808h17.jpg
It then looks like this. Can anyone offer me some help? Or has anyone had the same problems?