iPhone 3G speaker is not working

Hello,

I bought a brandnew iPhone but it seems the speaker(s) are not working. i just the forum search but also google and read about masses of people complaining about the speaker problem, but i think mine is a little bit different.

i dont hear:
- system clicks
- alarm clock sound
- ring tone sound
- message sound
- youtube
- ipod

BUT, i hear:
- talking with people on the phone (i hear them over the speaker!)
- i can call people and hearing the telephone sound
- i can record a voice memo and hear it WHEN i tap the speaker button in the upper left corner.

my conclusion is that it is not a hardware fault, since the speakers are actually working.

what i tried:
- the headphone trick. plugged / unplugged the jack at least a 100 times.
- clean the headphone jack.
- complete system restore.
- update 3.0 to 3.0.1.
- reset all settings.
- putting it into recovery mode and install everything from scratch.

does anyone have any ideas?
i think it is a software problem, but since i did a full reinstall of the OS this also seems not be the issue...