First, never attempt to reset your focusing with a zoom lens. My 70-200mm f2.8 Sigma has a close-focusing error at minimal focus distance, and this was causing me to screw up my attempt to reset my AF system on my D300. I was zooming in on something close (to better see where the area of sharp focus was). Once I went to the Nikon 50mm f1.4 body, things went much smoother. Now I'm getting pretty much laser-like images, all the way down to wide open settings, so I'm much happier.
Second, using single-point AF in the dark sucks on the D300. Cars in the darm (on a lit track) must not offer as much contrast for a single point to grab onto. Eventually I went to the 9-point grouped sensor setting and began to get sharp photos. It's very frustrating switching through the modes and getting shot after blurry shot. The 51-point "3D mode" simply does not work well for cars. There's too much area covered by the points, and it often grabs focus on a point outside the area the car occupies, resulting in out-of-focus photos. At a track, where there's often a white wall visible in the dark, the Nikon AF will CONSISTENTLY find that white wall in 51-point mode. Grrrrrrrrr. 9-point AF works well. I'd love to see Nikon add a 15-point mode, where it adds 3 more sensors to the left and right of the 9-point square, for a more horizontal configuration friendlier to cars. I don't need the additional 6 vertical points of the much slower-to-focus 21-point mode. Pretty please, Nikon? Can I have this in the next software update? I'm sure no one is reading this blog.
Third, though my 50mm f1.4 is the sharpest lens I own by far, its incredibly-slow focusing system will NOT capture cars in real-time. I discovered this in Long Beach in April, at the Formula Drift event, and rediscovered it in Las Vegas last weekend. My cheap 18-55mm Nikon "kit" lens is faster (though not by much). As a result I wound up using my much heavier Sigma 70-200mm f2.8 lens through the night. Boy did this make my arms tired!
That's all for now!