Comment 51 for bug 892316

The problem I reported and several others have also encountered was indeed caused by the MGSE media player control/indicator extension, and the patches submitted here fixed this specific problem. If you're still experiencing similar symptoms to those described here, and disabling the extension does not cause those symptoms to disappear, it's likely that your symptoms, though similar, are caused by something different from this issue.

Just to note, if you're experiencing similar symptoms to these but they happen even when no audio is being played from a media player supported by the MGSE extension, it's definitely not related to this issue, as this issue only happens while audio is being played by a supported music player and the extension is actively running (the extension is idle while there are no supported music players running and does not seem to cause problems while it is idle).