On the MacBook Pro I'm using, every once in a while I hear the sound effect that plays when you delete something...I'm not sure what it's called (a sort of poofing noise). It goes away when I uncheck "Play user interface sound effects" in preferences, so I'm guessing it's not a bug. Any way to check what it's coming from? I have Firefox open almost all the time, but other applications change and the sound doesn't go away. Any ideas? Thanks!