I got a set of used Logitech Z-5500 Digital speakers recently, and they've served me for a whole month before giving out… not there's suddenly no sound emanating from either of them. I don't know what happened, I guess if it's a hardware malfunction it only one of them would've died out…
Not necessarily. It could also have been a driver issue, I had a similar problem once where at first the new soundcard's drivers worked OK and there was sound, but after a restarted the system next (a few days later) it malfunctioned and the SC couldn't recognize the speaker system any more…