I've gotten this error for a while and I have posted in a topic about the same issue, I have dealt with it since my last windows reinstall, and ya, it does really suck.  I have heard of people having issues with windows xp sp2, maybe try re-installing that, or reinstall windows.. Long way around but I've heard it works.
When you are in game I think you can press shift+w when racing to try and restart the sound drivers..  what sound card do you have? 
I've also tried a different sound card in my computer and the same problem happens.  I blame windows.