This happens periodically when I'm using my 2.2GHz MBP. I'm running 10.4.9. It's not exactly a freeze, but it's like a sudden stutter. I can still open and run programs, but when I click on a menu, it opens and the selection bar jumps all over the place wildly. And a sound plays over and over like an error alert that just won't stop. Also at this point the Dock locks up and I can't add icons to it or open anything from it. Basically it's like the whole system goes into permanent stutter mode and only restarting the machine helps. Disk Utility has verified the disk and permissions are repaired. Seems like a software problem to me but if something is corrupted, I don't know what it would be. I never have this problem on my desktop. I haven't been able to pinpoint when this happens but it *might* be Dock-related.