I had a similar issue with clothing. It would turn the mannequin skin black. I had some files that were pulling the wrong textures for some reason. They would pick up the texture of another skin/clothing file and try to use it. For example:
![](http://i46.photobucket.com/albums/f120/cheriem72/Sim%20Pictures/FunkySkin.jpg)
I ended up doing just what another poster suggested. Going through my files a handful at a time and narrowing it down to the bad files. It took several days but it fixed the issue. Point is, your problem looks like a similar issue only with hair.