Err, description unclear?
If the black bars are on the sides of the screen, but don't block the important parts (the field to the left where there are bullets, the numbers on the right), there isn't a problem, the computer does so to use low resolutions on fullscreen. Depending on the hardware, it may simply be unable to use the highest resolution available (crashes upon use). Mine tops at (as per DDC) 960 x 720, can't use 1280 x 960.
Now if the bars are over the game, i don't know the cause.