Speakers Not Working

Hi,
Recently my speakers just stopped working. I have ran dxdiag tests and Creative diagnostic tests and they say everything is ok. The speakers themselves are connected and function fine physically, i.e. they turn on etc. but when for example I try to play a Youtube video the sound will not work. Or when I play music from iTunes it clearly shows that it's playing but the no sound comes from the speakers.

This problem has occured once before and I fixed it somehow but I don't remember how.

The sound card is a Creative Sound Blaster Live series card and the speakers are generic Dell 2.1 speakers.

Thanks,
Van