OK, bummer! My debugging was buggy.... Those are only there for the moment to see where I am. My fastest encoder, according to the scope is running about 50-60 hz. So that may be the problem. I'm headed out the door, but I'll try to deal with it when I get back this afternoon and see how it goes. I am still skeptical though, since it was the slow encoder that first showed the problem, and I still cant see how it would go from 3500 counts in say 120 seconds, all the way up to multiple WORD stackoverflows in the same time from this issue, but maybe I just still dont see the big picture....