I have a related preferences issue. I've got both the CPU and GPU boxes checked, and the PPS Sieve for GPU checked, and the SGS for CPU checked. However, on rare occasion I will get sent a PPS Sieve WU for CPU. I abort them when they show up; it's a waste of time when the GPU version is so much faster. I think others on the main boards have mentioned this but I've never seen an explanation or solution.