Frequently, yet not always, the iPod focus starts behaving flaky.  Specifically, the volume slider stops operative properly.  When I slip it to shift teh volume, the change doesn’t “stick” on the screen.  Sometimes the volume will change, somtimes it won’t.  If I reboot the iPhone, it will begin operative scrupulously again.

 

The OS is up to date – ver. 3.1.2 (7D11).

 

Any ideas what competence be causing this, or how to repair it?