I got a group of presets from the internet recently and think that's when my trouble with 10.1 started. I could be wrong. I deleted them from my panel and still have problems in the develope mode. Sliders are very slow to respond, and sometimes the image gets very strangly segmented. Parts will have different looks and portions are in the wrong place. Very frustrating. What presets have you downloaded and were they recent? This is a real problem I hope Adobe can fix soon. Lightroom is almost unusable.