A strange error has occurred with my iPhone 3G S - If I play a video file in the iPod app, no playback sound is audible (this happens both with or without headphone plugged in).

When I've done this, all sound is gone from any iPod file (podcasts, etc), from the alarm function, voice recorded, etc - however textmessage sounds and ringtone, phone call, appears to be working.

Turning the phone off and on a few times - or doing a reset - restores back to normal, so I can play audio files, set alarms, etc - however, playing a video kills the sound again.

Anyone else experiencing this problem?

Any solutions?!?!