This one has me confused.
I'm not sure if the culprit was doing a Windows7 update today (hadn't done one in about a month). After the reboot or shortly thereafter there now seems to be no sound coming from the speakers.
When I did the individual sound test I did get the proper 'ding' test sound indicating that the sound is working.
Playing Winamp I receive a "Error creating DirectSound buffer. Error code: 88780096" alert message.
Windows Media Player/VLC/WM Classic all open and play properly without sound.

I thought a culprit could perhaps be "HD VDeck" (this uses a SPDIF Interface) sound system enhancer ... the self tests here seem to indicate that a everything is performing properly.

Maybe there's a wizard that knows the answer on this one ... thank you.