I have some mid-priced Logitech 2.1 speakers that had me thinking that once after an upgrade. Turns out they needed switching off and leaving unplugged from the PC for five minutes - just something in the amplifier circuitry playing up and it was coincidence. I suggest you try the same, might not work but unplugging/replugging/rebooting to double check it's not hardware/transient is a good sense first move with anything computer. With GNU/Linux being so reliable you have to do it less often and it's less often the culprit, but it's still first base IMO.
Leny
