I recently bought a set of Logitech ClearChat wireless headphones with USB dongle (model A00006) to use with my MacBook Air running OS 10.5.7. They record fine, but on playback the sound is constantly broken, producing a horrible crackling effect. I rang Logitech tech support to ask for a new set, and they asked me to try it in my desktop, an iMac, where it worked fine. They then claimed it was a faulty USB port on the laptop. However, I have now had the laptop thoroughly checked out and no fault has been found. The retailer where I bought the laptop claims that the headphones are simply not compatible with the laptop, though Logitech publish no compatibility lists. I have tried downloading the firmware update at http://forums.logitech.com/logitech/board/message?board.id=headsets_general&thread.id=5859, but was told that it had already been applied. Any suggestions, please?