Sorry for all the questions today, it's the first time I've given my MBP a good workout. So far it's behaving like a champ but I've gotten the same problem twice today and I'm not able to find an answer for this. What happens is I will go to the Dock to open or switch to an application, and nothing happens. (This is after a good amount of time when it works fine.) I'm also unable to drag an application to the Dock. When this happens, menus also go crazy -- that is, when I right-click on the Dock or pull a drop-down menu, the options blink back and forth quickly without my being easily able to select one. Does this behavior sound familiar to anyone? It's happened twice in about two hours, once on battery power and once plugged in. Both times a restart fixed the problem immediately. I've been using Mail, Firefox, Word, and iTunes. The first time the problem cropped up when I tried to drag an application to the Dock; the next time it happened when I tried to switch to Mail. Thanks for any ideas and sorry about all the questions today. I'm using a 15" 2.2GHz SR MBP running 10.4.9.