hi there i seem to have a problem with my sound . one min it will work fine then it just shuts off on its own . the radio and cd wont deliver any sound at all . they function but no sound . today i was using the sat nav built in on the instruction screen and the music shut off again now if i click on intruction to make the woman spk or she spks herslef it comes back on again . its driving me mad . has anyone got this problem ?