Zero, have you downloaded the latest? Because Layer FX are up already, you know.
The "dirt" sounds weird, but I wouldn't be too surprised. I haven't had it, yet, but I know I'm doing a risky procedure there, which has potential to do some funky nonsense. It doesn't "smooth", it averages! That means, it grabs the paint under the brush, subtracts the pixels outside the brush radius, collapses it to one pixel with MIB mapping and then uses the resulting color as color to paint with. This is a bold approach, but fast and generally reliable.
I know, it's a tall order, but if you have some way to provoke the problem, let me know and I'll try as hard as I can.