Update - The title of this discussion has been changed in light of the solution found in the comments below. Thanks to Weaselboy for helping me discover that El Capitan didn't do any automatic repair fix following the 10.11.1 update. This resulting in the problem below: I've tried reboots and removing log in items. Nothing helps. After yesterday's update UserEventAgent hogs the CPU, staying at 99% the whole time, and sends CPU temperatures 10 degrees centigrade higher than normal.