are you able to open up the volume panel of windows and are they reconized by windows and used for a application such as mediaplayer..that will give you a idea if they are bad,,,not shure what software you are using for U-Mix,,software badge not regerstered,,,have you opened options and audio in home and see if the correct selection of sc is present,,have you done the same for Cross and see if they are reconized and selected for use,,,
if the options come to getting another sc kev mav had/has posted a relitive inexpensive sc that he has feild tested with promising results,,,,
a little bit more info might help,,are both sc the home 7 sc,, and the U-Mix is the one without the installed sc