I bought a Kindle Fire about a year ago and I'm really pleased with it, BUT on the three occasions when I have downloaded an app it has caused the system to mute. even tho the volume shows that it is at maximum there is no sound at all, whether for YouTube, music files or notification sounds. Nothing. Sound returns as soon as I uninstall the app from the device. Does anyone else have this problem and if so how can I get around it? I'm loath to send it off to be examined/repaired. 

Thanks for the advice, everyone!