Black stuff blowing out of vents

My 2001 626 v6 has started blowing black stuff out of the registers either when using my AC or when it sits idle for any length of time. When I picked up a piece of it and crushed it in my hand, it would disintegrate into almost a powder-like substance. I looked into the registers (my center registers oscillate) and saw a large (1 1/2 inch x 1/2 inch) piece of a black net-like substance that was blowing against the back of the grille of the center and driver's side registers. I had to use a cotton swab to get it out while the AC was blowing (it would fall back into the vent if I turned off the air flow). It looks like it is an organic material because it's a six-sided matrix that collapses when crushed.
I took it to my mechanic and he said it was probably the insulation foam the factory puts between the vent pieces in the air duct system but that he would have to take the whole duct system apart to see if that's it. I don't think that's right because it is so easy to break down when it's crushed in my hand. Someone told me that it might be a mold or fungus that is growing because the AC condensation pan is clogged and not draining, but my mechanic said my car doesn't have one of those. All I know is that there is black crap all over my car because it's blowing out all over everywhere and I'm tired of cleaning it up. I also don't want to be driving it if there is mold or fungus growing in the ventilation system. Just the thought of it makes me itch!
Has anyone ever heard of this or does anyone have an idea of what it could be? It's not affecting the performance of the car and the AC seems to function just fine. It just started this summer (that started out really rainy) so I don't know if it does it when the heater is on. Thanks!!!