Master Mute Problem

Hi

I have an Inspiron 4150 just over one year old.  Very recently I have had a problem with my audio. A flashing signal saying 'Master Mute' turning alternately red and green down the bottom of my screen appears every few seconds.  When I go into my sound & audio settings I notice the the 'device volume' mute box (where you tick it for either off or on) automatically turns itself off and on in line with the flashing on my screen.

Wondering what is wrong with the audio device and whether it can be easily fixed.

Thanks

Nick