Volume buttons not working on iPhone 4
I have an iPhone 4 running version 4.1 (8B117) software, and have noticed that the + and - volume buttons do not seem to have any affect on music or call volume.
When I plug the headphones that came with the iPhone, the volume buttons on the headphones control the volume (in iPod mode the slider moves up and down, along with the volume), and when the iPod isn't playing music pushing these buttons brings up the volume icon, again changing the volume as you would expect.
But take the headphones out and try to use the volume buttons on the handset, and nothing happens - no moving volume slider, no volume icon, and no change in volume.
Dose anyone have any ideas - phone fault, settings hidden deep in a menu structure etc?
Thanks
Paul
iPhone 4, iOS 4