Please take the time to read through this thread: http://www.emutalk.net/showthread.php?t=19894
To get you started, yes it looks like a graphics problem. CHIP8 sprites are drawn with a simple XOR rule. This means that if a solid pixel is drawn over a solid pixel, the pixel will be erased.

> Ok, here are some pictures of chip 8 emualtor I programmed.
>
> http://i2.photobucket.com/albums/y6/pradipna/chip81.jpg
> http://i2.photobucket.com/albums/y6/pradipna/chip82.jpg
> http://i2.photobucket.com/albums/y6/pradipna/chip83.jpg
> http://i2.photobucket.com/albums/y6/pradipna/chip84.jpg
> http://i2.photobucket.com/albums/y6/pradipna/chip85.jpg
>
> The problems are in graphics.
>
> I programmed it in VB so if anyone could I would appreciate that...
>