Cant use soften brush in texture paint mode

Support Materials and Textures
1

Hi, I have been texture painting this same way for several weeks with great results. However today I am having some kind of glitch. There is a tiled skin texture with 3 other textures set up to alpha over the tiled texture. The other 3 textures are for details like freckles and stuff. when I try to soften the layer that has color and alpha, the whole texture goes black in that area I have attached a screen shot that shows the setup. Any ideas?

soften
soften2048×1077 560 KB

2

soften2
soften21047×532 142 KB

Changing the aplha setting in the UV window from pre multiplied to straight seems to make the problem go away. It did not matter which mode I used. I think switching it just made blender re load the alpha channel.