Wireless streaming causes OS X to crash.

[Farmer Pete]

Hello I have a Mac Pro running OS X 10.5.7 and iTunes 8. I have an Airport Extreme and an Airport Express in an extended network. The music streams to the Airport Express connected to an Apple stereo system.
The music starts well and lasts maybe up to 5 minutes and then Mac OS X quits, leaving a screen notice that OS X was forced to close. This happens every time I attempt to stream music.
I have tried many different approaches including phoning Apple Care. The Extreme is 'n' series and the Express is 'g' series.
I really want to fix this problem as it has got under my skin. Tonight in desperation I decided to try and stream using an old Dell pc and iTunes. It worked perfectly and is still working several hours later. Unfortunately my music collection is on the Mac! Given that the pc worked I deduce that there is nothing wrong with the Airport Express or Extreme or the Apple stereo and that the issue must be related to my Mac settings or iTunes. I have trawled the web sites and forums but have not found an answer.
Any insights would be greatly appreciated.
Cheers.

[Satcomer]

When the Mac quits immediately launch /Applications/Utilities/Console and see what the logs tell you about the crash.