How are you viewing the video when you see it jerking? If it looks OK in the camera then it could be a playback problem on your PC, because the Canon HD mov files need a good processor to play smoothly.
But if the camera playback is also jerky, the problem is in the footage itself. If you are shooting 25p you need to make very slow camera movements, because the frame rate is too low to capture fast motion smoothly. Also you could try to avoid having subjects move at right angles to the camera direction. Moving the camera to catch the motion on a diagonal line, to reduce the effective angle, can help a lot.
One alternative solution is to shoot 50p (at 1280x720 resolution) but the aliasing artifacts on this cam can be quite rough in 720 mode.