I have an iMac running Lion, with an M-Audio NRV10 attached by firewire. All the latest patches for everything. iTunes and all other apps playback through this system fine. Both Logic 9 and Garageband have some clicky type distortion on playback. It sounds like clipping but doesn't show anywhere. Audacity records and plays back fine also. Both Logic and GB have this problem with demos supplied with them. If either Logic or GB are loaded then iTunes exhibits the same problem, but is fine if loaded alone. It helps to reduce the buffer size in Logic. It's driving me crazy. Any ideas?