i've used my 70-200mm VR with the SB-800 as fill light several times without any problems, but this is in daylight or in the shade. you shouldn't have a problem using VR at slow shutter speeds and firing the flash at the same time, but keep in mind that you'll still get subject motion if there's enough ambient light to overcome the flash. this can lead to some pretty neat effects.
Well first of all, vr controls camera shake not people movement. When using flash, shutter speed is limited to the sync speed of the camera. For my D2H that is 1/250th of a second. Flash is very fast but as has already been pointed out ambient light will still allow you to see movement with people if your shutter speed is too low. What I am trying to say is that your vr plays only a minor role in the whole scenario.