Missing SMSMMS Alert Tones iPhone

Just did an iPhone 3Gs hardware swap last week. Restored from last session.
Have not been able to get iPhone to play any of the audible SMS/MMS alerts since the restore.
Side switch is not in vibrate mode. It is set for audio.
Alert volume is set for max.
In the Settings - Sounds - New Text Message menu you can select the following alerts:
None
Tri-tone
Chime
Glass
Horn
Bell
Electronic
Selecting any of these sounds does not produce an alert tone.
Has anyone else experienced this?
Is there a known work-around?
Thanks
iPhone 3Gs iPhone OS 3.1.2