I have one of those strange issues that is really difficult to diagnose, so I thought I would check and see if anyone has heard of this before or has any ideas. I have a late 2009 i7 iMac to which a Mackie Blackjack is connected via USB. I am running the most recent version of Mountain Lion. I have a pair of Klipsch computer speakers w/subwoofer connected to the Blackjack. The Blackjack has no drivers, it uses core audio. Every so often (I can't find a pattern) when audio is starting (e.g., I hit play in iTunes, a mail message alert comes in, etc.) I get a burst of static white noise. After that the audio plays fine until the next similar event. The Blackjack works fine for recording. Annoying issue to say the least. I have connected the speakers directly to the computer using the 1/8 " jack and the problem does not seem to occur. I have also disconnected the speakers and listened through the BlackJack headphone jack and I still get the white noise on occasion. I can't figure out if there is a hardware problem with the Blackjack or if there is an operating system issue or incompatibility. This has been going on for a while and I don't recall when it started (i.e., whether it was related to my upgrade to Mountain Lion). Unfortunately I don't have another audio interface to try and I don't really want to buy one and then find out it wasn't a problem with the Mackie. I spoke with tech support at Mackie and they are not aware of any other people having this issue. They said that the Blackjack hasn't been technically certified to work with Mountain Lion, but it should work just fine. Any ideas?