Comment 38 for bug 1067434

If someone reaches this page again with this problem, try this:
Install alsamixer if you don't have it installed.
Open a terminal and execute the command below:
alsamixer -c0
this will run the alsamixer, use the left/right arrows and find "loopback" option(Usually it's on the right side). When you find it make sure it's disabled, if it's enabled, press the "down" arrow to change it to disabled. When you did this, press ctrl+c to exit alsamixer.
Check and see if the problem is gone or it's still there. It should be solved.