So yeh, at least once in every 2 weeks I'd get this sudden flow of white noise generating through the session. It would just happen out of the blue. One moment I'm scrutinizing the mix, the next moment I've got my ears covered in horror. It was pretty rare and easy to get over with. All I'd have to do was restart Pro Tools and it would be gone. Once in every 2-3weeks was tolerable enough. But the last time it happened (a few hours back), the tweeter on the left channel died on me. ARGHHHHH! 
