Hair sprouts elsewhere

I have done this before on making particles for hair and it worked fine, but just recently when I put particles on the head for hair and particles worked fine, but after I comb it and return to object mode, the hair is fine, it is when I render it that hair sprouts all over my model where there were not vertex group assigned. is there a bug in blender? I have done several models and it worked fine.

post an image, if you think it is a bug, please report it…

Before combing the hair, click the ‘Use modifier stack’ in the Emission section of the Particles Tab. Note that once the hair is combed, this option is not available.