iPad 2 volume switch not working

[ascender]

Wife has a new iPad and unless I'm missing something really obvious, the volume rocker switch isn't working. When you press it up or down, the bars come up on screen and correspond to the switches, but the actual volume doesn't go down or up at all. Turn it all the way off and nothing, although the mute button does work.

Any ideas or is it a trip back to Apple when there's stocks available?

Thanks!