Phone hangs when increase/decrease volume, help please.

My phone hangs whenever I press the two buttons at the upper right, the Check Phone status button .. When I'm using Media Player to play songs and I press those two buttons to increase/decrease volume, my phone just hang there and after that, no matter what I press, it just won't give any response at all, it just stuck there with the keypad light up forever until battery runs out unless I remove the battery to shut it down ... Anyone knows how to fix this ?

Have you done any...strange update or customization?

Try A Full Reflash. It Should Solve Your Problem Cause Its NOT A Hardware Problem. See XS++ 3.1 Guide-Flashing,Customizing,Recovering - Top Sony Forums