The simple material room is meant as a fast way to apply textures to models.  It is meant for the novice or someone who does not want to enter the advance material room (Edit).  It works in two different ways.  1 is for the background and with the background selected you can move between simple and edit with no problems.  2 is for everything else.  In #2 you have to select the material that you want to change (such as La Femme Skinhead) and then press the Create Simple material.  This activates the simple material and applies it to the part you are working on.  You can NOT enter the edit area (for that material group) once you start a simple material UNTIL you either A) Reset Material or B) Create Advanced Material, at which point the simple material tab reverts to waiting for you to press the Create Simple Material again.  Again, this for those who do not like to enter the Edit area (Advanced) of the material room. 

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13, 14