I have used task manager to observe the CPU usage while the audio was on, and noted that memory usage escalates gradually over about 5 minutes to 100%, at which point the system crash occurs. If I turn off the messanger programs before the crash - then CPU usage goes back down to ambient levels.
I have tried a number of things: disabled firewall and virus protection, adjust audio acceleration setting, upgrade audio driver (SoundMax Integrated Digital Audio), and Direct X to most recent version (9c), checked for hardware conflicts... etc.
Nothing has solved the problem. If anyone has any other suggestions, I would be most greatful.