Lost sound on my Xperia X8? I'm having problems with my Xperia X8, where it doesn't have sound from it's speaker. 
No phone sound, music, games, and even alerts.

On the sound settings, the volume settings are set correctly.

Sound is coming fine while making calls, both ways.

It is even giving proper sound with headsets but sound is not coming from speakers.

Torubleshooting: Restarted.... Given soft &amp; factory reset, but no luck.

(Android 2.1)
I too had a same problem on Xeperia X8. I guess the cause was I kept on downloading the android apps without restarting the mobile for months. After experiencing similar issue like you I have just restarted my mobile, did not revert any settings to default or upgrade OS to latest. 

It solved !!.