My sound was working fine last night, no problems at all.. then I woke up today trying to view something on youtube and no sound :\

What works:

IM Sounds, In-game sounds (WoW, Dragonica, etc)
Sounds/Music in chatrooms (Yahoo/Camfrog)
Error sounds on my computer

What doesn't work:

Youtube, ANY music (including songza.com/mixturtle.com)
Music on my hard-drive

Any help?