I have the speaker problem... and this is my story:
The first time my speaker sound disappeared was when i was talking on the phone with the earbuds (headset) plugged in. When I ended the call with the squeeze remote, the ipod mysteriously started playing the first song in my music library on the iPhone. I disconnected the earbuds (without turning off the music) and the sound disappeared!
I did a restore on the phone... and "voila!" the speaker sound returned.
A couple of minutes later I was browsing the content on the phone (AFPd from Installer) while listening to music on the speaker. I closed the server connection... and the speaker died AGAIN!!!
Frustrated I started to fiddle with all the buttons. When I dubbel-tapped the power/mute button on top of the phone, the speaker activated again!? Nervous as hell I pressed the power button again to make sure the speaker sound should stay on this time... but no, it disappeared. This time for good!
To this moment I have tried:
* to clean the female end of the plug from dust with a cotton swab
* reset
* restore
* virginize
* oneSim (some had problems with sound disappearing when using anySim)
* update to 1.1.2
...still NO speaker sound!