i was on skype one day and after being put on hold for about 5 minutes my webcam went off, it wouldn't turn back on and it kept saying playback malfunction or something like that and from then on the sound hasnt been working on my laptop either.
More aboutlaptop playback sound working dell
does sound and webcam work outside skype? (http://www.testmycam.com)
if it does its a skype problem, if not its a driver (device manager - reinstall driver by removing and restarting system) or hardware problem (warranty or live with it)