Dirt shader doesn't work in progressive?

Oso3D

http://www.daz3d.com/daz-studio-dirt-shaders is really nifty for grunging up textures in 3DL.

Except... it doesn't seem to work with Progressive rendering. It looks fine on the first and second pass, but on the third pass only the primary texture is displayed (not the dirt that should show through)

Now, that's not the end of the world -- I can make sure the object looks cool, then set up my scene with Progressive until I like it, then switch Progressive off. But it's... weird and a little inconvenient.

(On a separate note, anyone know a way to set up this dirt shader to work on transparent surfaces, like windows? It'd be great...)