It's a little difficult to know what is wrong. Is this dynamic hair you have grown from a pre-existing scullcap or are you growing it directly from the figure's head? The problem you describe sounds much like "polygon overload". More polygons equals more hair and this in turn makes your computer have to calculate more collisions. Another factor that causes a slow-down in calculation is the figure itself. The hair has to also calculate collisions on the figure's polygons, so the more polygons a figure has; the slower the calculation. Also, the longer the hair, the slower the calculation. Something that might help in explaining this is some hair available in the freebie section called "Genesis Hair for Jessi". Follow the enclosed tutorial and it should work on your computer. If you look at it in wireframe mode, you will see that the scull-cap and proxy figure are made up of only a few polygons which helps to lessen the time needed for calculation. Hope this helps.