My Latitude E6500 notebook is periodically muting while on battery power. The mute is invisible in that it doesn't show as muted in the system tray, and the only way I can unmute it is by changing the system volume. It happens at least once every few minutes, so it's devastating while I'm watching video or listening to music. What's going on???
This just started happening in the past couple weeks and I've killed all new programs and processes I've recently installed, and by its behavior it seems to be a hardware or Windows issue since it only happens on battery power.