I think I used to know how to fix this but my technique isn't working.  Seems to me I could just go into the material room and click the Image_Source and then the hair would reappear.  But it's not working with Sensual hair for V4.  I just hacked the CR2 to change all the displays to TEXTURESHADED so that's not it.  It shows up fine, then I apply a MAT pose and it disappears.  It's still there, just invisible.  Arg.