"Apps" can be buggy and this is a bug I've seen before. Call it in and see if they have a fix or a fix in the works.
I've got an LG 60PM6700 hooked to a Bose Cinemate system through a digital optical cable. I've got the tv speakers set to off. Just watching TV or a movie and the sound works fine, the sound on the apps works fine (Netflix, Hulu, YouTube, etc.) but if I use the built in internet browser and go to an actual URL like Pandora for example I've got no sound through the Bose. If I turn the TV speakers back on then I can get sound through the TV. Any ideas? As I said, the external speakers work for everything (tv, apps, etc) except the internet browser.