Information for Mac Users

Apparently there is a glitch with some Macs and the program Quicktime, which is an Apple product.

Some applications may output no audio, but system alert sounds and iTunes playback can be heard

This can happen on Macs that support high sample rates (higher than 48000 Hz), including these:
   MacBook (all models)
   MacBook Pro (all models)
   Mac Pro (all models)
   iMac G5
   Mac mini (all models)
   Power Mac G5 models that support sample rates higher than 48000 Hz
   PowerBook G4 support sample rates higher than 48000 Hz
   iMac (Early 2006) and later
   Some videos/movies  will play the video but no audio. '

The best option is to just download and use VLC Media Player for Mac

http://download.cnet.com/VLC-Media-Player/3000-2139_4-10210434.html?tag=rb_content;contentBody;pop

another option : http://www.perian.org/  .

   Perian enables Quicktime to play a variety of formats with both video and audio. But you need to have OS Tiger or later for it to work