I had the same problem and discovered that my son had plugged the audio jacks the wrong way in.
Check it, maybe it's the solution to your problem.
All of a sudden I'm not hearing audio on web pages on the 'net. This doesn't apply to streaming audio but it does apply to mp3's that play online and to audio on videos, such as Camtasia videos.
Now the important point to understand is that I've had audio on these specific pages previously, so something has changed to cause me not to have audio now.
Any idea what's going on and how I might correct this?
Thanks in advance for your help.