Help with playback stutter in Sony Vegas Pro 11
I have seen some trainwrecks by combining Nikon .mov with Vegas Pro 10. After tech calls into both Nikon and Sony it was determined that my machine didn't have enough resources.

I need to upgrade from 32 bit to a 64 bit version of Win7, plus I need to go from a quad core to an i7, and from 4GB to 12 GB or better. I can use my Nikon files now but only if I keep the total under 1 GB, short projects only but it works. One thing that may help your stuttered preview is to set the window to preview mode at 1/4 size, this helped a lot for me.

Here is a tutorial that covers everything I've tried and more of the things that may help you
get your playback smoother.