Yesterday my parents' mac started acting up. It won't autoshow the dock when the mouse is moved down to it, hot corners are disabled (but enabled) and the cursor will not mark whatever it hovers over (the bubbles in the corner of apps, drop down menu items are not blue when the mouse is over them, cursor won't change to show that it hovers above a link in safari etc. etc.). It's quite annoying. What should I do/remove of plist files?