Andy L , Feb 21, 2009; 12:48 p.m.
Tell us about what ISO, F-Stop and shutter speeds you're using. You want to make the shutter faster, which you can do by increasing the ISO and decreasing the F-stop (widening the aperture). The D90's high ISO performance should give you good shots at 1600 or even 3200. Try shutter priority mode at 1/1000 and faster. See if you can get focus tracking in continuous mode.