Sound lost on FC#

[ice]

hi!
 I'v a very strange problem related to fc3, yesterday fc3 was playing sound
perfectly, but when i today bootup my system and after installing some
development tools, try to play my favorite song list, ,, i get no sound,
sound is all lost, i tried to reconfigure the sound card, but it fails to
produce sound,,
 i fail to understand that how sound without any reason lost....
 please help me......