You might be one of the victims of the Vuvuzela Horns. Since the offical don't plan to ban it, we just silent it ourself.
Folks over at Lifehacker have found that if you adjust your EQ at 465Hz and 235Hz, you can in fact filter out the buzz with great results. Ideally you'll reduce each frequency by at least 40dB (which got rid of the drone completely for us), but if your equipment can't quite adjust that low, just go as low as you can.
Check out the demo video clip - How to remove Vuvuzelas by Lifehacker!