Gub,
Are you using the audio drivers from Windows Update? I would not use these. There has been many reported problems with using them. Instead, I would use the ones directly from Realtek. You have to install it twice and reboot between each install. Once to uninstall the old drive, and twice to install the new driver.
http://www.realtek.com.tw/downloads/downloadsview.aspx?langid=1&pnid=14&pfid=24&level=4&conn=3&downtypeid=3&getdown=false
Shawn