iPad mute switch doesn't mute on iOS 4.2.1

After my iPad upgraded to iOS 4.2.1, the hardware switch that used to lock the screen is now not working.New mute switch just shows "mute" icon, but doesn't mute. When I switch to the up position, it shows a speaker and the current volume. And switching to the down position shows a speaker with a slash.The mute switch won't mute music or video. However, it will mute apps and push notifications.