I've been experimenting with Pixel Bender since I got it and have slowly made my way to creating somewhat simple filters. I've also been using them with flash for quite a while. And I seem to have found a bug or something. Inside the evaluatePixel function, try putting just the following:

dst = sampleNearest(src, outCoord());
dst.b = (outCoord().y / 40.0) - floor(outCoord().y / 40.0); //used to have mod here, thought it was the problem... it wasnt
dst.g = floor(0.8);
dst.r = (dst.r * 4.0) - float(int(dst.r * 4.0));

Run the filter on an image. Now load the same image into flash, load in the filter with URLLoader and make it a shaderFilter. Then apply it to your image. You get something different. In the actual filter that I was trying to debug I got a completely different result using the exact same code as up there.. (that one had vertical green lines running the entire height of the image, spaced out once every 4 pixels. Same code, but those lines don't appear in this filter.) What's the problem here?

Mavrisa