Lost Sounds, iPhone 3G -- on 3G

[KJB]

The sounds (keyboard clicks, send mail sound, text & e-mail received sounds) disappear when the iPhone 3G is operating on the 3G network -- it is fine under the wireless network. 

Help, please.  I missed a couple of important txt's this weekend.

Thx.

***Edited to add labels***

[FidoJean · Accepted solution]

This sounds like some sort of software corruption. There is no option I know of to disable specific sounds when on//off 3G. Have you tried turning your device off and on?

You may need to perform a restore using iTunes if the issue persists.