I lost the sound for all apps. Music plays fine but apps do not have sound?

If you lose sounds for keyboard clicks, games or other apps, email notifications and other notifications, system sounds may have been muted.

System sounds can be muted and controlled two different ways. The screen lock rotation can be controlled in the same manner as well.

Settings>General>Use Side Switch to: Mute System sounds. If this option is selected, the switch on the side of the iPad above the volume rocker will mute system sounds.

If you choose Lock Screen Rotation, then the switch locks the screen. If the screen is locked, you will see a lock icon in the upper right corner next to the battery indicator gauge.

If you have the side switch set to lock screen rotation then the system sound control is in the task bar. Double tap the home button and in the task bar at the bottom, swipe all the way to the right. The speaker icon is all the way to the left. Tap on it and system sounds will return.

If you have the side switch set to mute system sounds, then the screen lock rotation can be accessed via the task bar in the same manner as described above.

This support article from Apple explains how the side switch works.

http://support.apple.com/kb/HT4085

I had this same problem and thanks to your suggestion and guidance it worked.... Thank you!

I had the same problem after installing the IOS 5.1 upgrade,but discovered how to fix it. The problem is with the slide switch, if you go into General settings, and find that the slide switch option is set to screen lock, this causes the problem. Just select the Mute function , then make sure that the slide switch is in the up position , and you should find that all your Apps work perfectly.

Thank you so much. I was just getting ready to go to the Apple store. This suggestion worked just fine.