Ok, so this is really weird. It's as if OS X has stopped tracking the location of my mouse, only keeping track of it the first time an application boots up or when I click with the mouse. What I mean by this is that alot of things that are based on mouse positioning (tooltips, dock app labels showing up, menu highlighting, displaying image alt-text on websites, showing the proper cursor icon based on context) DON'T work properly EXCEPT for when an app first boots up (so if my mouse is hovering over the close/minimize/resize buttons when it first boots up, the labels will appear, although they won't disappear until i click elsewhere) or when i physically click with my mouse, at which point OS X recognizes the mouse as being at the point of wherever I clicked... until I click again. This produces really weird behavior - using menus is weird as if I click on one menu item and then click on another, the second menu item will drop down into its submenu but then immediately disappear (as if I had clicked twice). If I'm editing some text and try to close the window, the cursor remains as the I-bar insertion cursor until the moment I click, where for a split second (as the window closes) it turns back into a normal cursor. I can't read Dinosaur Comics's second joke (which you get by hovering to get the alt-text of the comic's image) unless I physically click on the image, THEN wait and hover. And I get really weird tooltip behavior: tooltips will appear for items that I'm not actually hovering over - so long as I clicked on it before and then stopped moving my mouse (as if I was hovering) before having clicked on something else. I repaired permissions, I tried logging in as other users (i also have a guest and admin account), I tried rebooting, I tried safe booting, and none work. Interestingly, while I was typing this up, there was a very brief few seconds in which everything worked fine again (at which point I left this page and lots the message I had been writing) until after about 10 seconds it flared up again (at which point I had to retype this message grrr). Help!