I have this in Mac OSX 10.8.5 as well and I suspect is has something to do with sleep/hibernate/standby and/or turning off and on the controller while a MIDI program is running. Arturia has known about this for a while now and in several forums have said they're working on a software or firmware fix - last year. Guys, I'm sorry to say but it's obvious they don't care about Laboratory users. It's all about their new products. They discounted these packages last year to boost sales, but we haven't seen any software or firmware updates to solve the plethora of problems Laboratory users are having. I like the software and the feel of this controller, but this many bugs makes me wonder if they did any testing at all.