<S> I used to have Logitech and problems as many of you are with calibrations/ spikes. Logitech has on their website a "Clear Calibration" utility. You might have to dig around on their website, but its there. Run it. It took care of all the issues. What happens is, your calibration will. as you calibrate more and more, become fragmented. This leads to the spiking/ poor calibrations. Hope this helps you all, as it did me when I had Logitech sticks.
S! Oz