I have been having the following issue with my 2009 i7 iMac for the last few months. It is an irritant, but is gradually becoming maddening. Specifically, if the active window has a vertical scrollbar, it will start scrolling down automatically and won't stop until it reaches the 'bottom' of the window. You can pull the scrollbar back up from there, but it will immediately scroll down again. It doesn't happen all the time - it can occur from 1-2 times a day to once every couple of weeks, but once it gets triggered, only logging off or restarting will clear it. It has persisted over multiple revisions of 10.6. I am using a Wacom Intuos 3 tablet and a Magic Trackpad, and no mouse is active on the system. The scrolling issue occurs even if I unplug the Wacom tablet and turn off the Trackpad. There may also be some sort of x-mouse component - when the problem occurs, the Twitter for Mac window will become active if I pass the mouse cursor over it, but I don't think this applies to all windows. Also, the problem seems to occur more often in conjunction with iTunes (sometimes it will trigger right after I quit iTunes, for instance), for no reason that I can fathom. Anybody seen anything like this before? I'd do a fresh install and migrate my data, but am afraid that would just reimport whatever the problem file is - please let me know if this fear is unfounded. Thanks for any pointers or hints you can give me.