Unable to adjust volume on iPhone 4
My iPhone 4 has developed a strange fault. Sometimes when I try to adjust the volume, either with the hardware buttons or using the software interface, the phone registers that I'm changing the volume but it doesn't actually get any quieter (or louder). The problem is the same whether I'm using the headphones or the speaker.
The only way that I can resolve the issue is to turn the phone fully off and then reboot it.
I think this issue only happens once the phone has been connected and then disconnected from my in-car bluetooth handsfree system, although I haven't exhaustively tested this yet.
Anyone got any ideas?
Thanks in advance,
Tom
iPhone 4, iOS 4