Ok, this is so weird...I have and iPhone 3G, 16GB. I can hear anything when I'm on a call, have sound on headphones (you tube, IMS samples, songs), have ringtone on the speaker when incoming call, while over a call I can hear over the speaker, and can hear ringtone sample on the speaker when setting up the volume, but THERE IS NO SOUND over the speaker when playing music, watching a YouTube video and the locking and typing sounds. I've tried the plug and unplug headphones hundreds of times, cleaning the headphone jack, resetting all settings, restore to 2.2.1 and it's not jailbroken. I would appreciate any other suggestions; by now I don't really care about the iPhone, I just want to know how to fix it and what could have caused it. Thanks.