Use a Titanium G 4 867 with OSX 10.5.8 Leopard. After upgrading to Leopard operating system from Tiger I began having issues with my ITunes hanging up on me. I don't know if this was a coincidence that this started shortly after installing Leopard or not. This problem arises when I'm using Youtube as well. There will be times where the sound performs without a problem then suddenly starts having issues and begins to hang or cut in and out. Use headphones a lot and when this starts happening if I take the headphones out of jack it tends to activate the audio again. This may only be for a brief moment sometimes then it freezes/hangs up again. Someone with any ideas or similar problems in the past please let me know. Need to narrow the possibilities.

Maybe it is your iPhone'problem. you can ask an expert for this problem

Does this happen only when you use your headphones? It sounds like it could be a problem with your headphones.

Nope, I don't think so. Recently upgraded my G5 to 10.5.8 and also getting the same problem. Happens with BBC iplayer and youtube for me. Have to refresh the webpage to get sound working again. I have a feeling that sound is cut out the loop on streaming media with 10.5 if the bandwidth drops.