It won't play in 1280x1024 resolution

I have a 1280x1024 resolution and for some reasons, bsplayer won't play any of my movies(especially *.wmv files) in the resolution mentioned above. Each time I play a video file, all I see are bunch of coloured and black lines. I have to change the resolution(from the video option) to 1024x768 so I can see the movie. I would appreciate any help that you can give me to resolve this problem. Thanks