text from guitar hero forum...
Response 10/31/2007 12:56 AM
Hello and thank you for contacting Activision Customer Support,
Yes we are working on this issue and ask for your patience at this time. It does in fact seem to be a Wii only issue. Information regarding patches for the Wii will be posted on the Guitar Hero III website when the appropriate time comes. Please try setting your console to use stereo sound in the meantime.
Thank you for contacting Activision Customer Support, if you have any other questions, we will be happy to address them.