My iPad speakers don't work...

Hi all, my iPad 3's speakers stopped working yesterday. It's not a hardware problem, because some apps run sound through speakers and some don't. Headphones always work. How can I fix this? Yes I've restored and yes I've set it up as a new iPad to no avail. And I have the sound up full on all apps. I think this is a software problem, as one of my mates has an iPad 3 on iOS 6.0.1 like me, and he has the same problem. Any suggestions?