What sort of settings do you use to capture fireworks? Since I've got this Canon SLR I don't have a clue, I just used to use the Casio point and shoot, that had a 'firework' setting.
Most of them were shot on manual with f8-16 aperture and then experimented with shutter speed from 2-10 seconds. Focus was set to manual, and distance to infinity and had the camera on a tripod.