Samsung Galaxy S II :: Games Freeze If Turn On The Sound?

I found many games include: greedy pigs, catoon defense 2, battle heart, etc ... (I purchased from android market) will randomly freeze during the game play if I turn on the sound! However, if I turn off the sound (I mean turn off the sound option in game, not mute the media volume), then all games runs without any problem.

Not every game will have this problem. For example, angry birds, finding difference, air attack, etc... No problem at all. It looks to me that most of defence games and real time strategy games are in this case. It's just the game itself freezed, not the whole system. I can still use "home" to go back to the main screen then kill the game app.

I'm using vodafone version s2 and already updated to the lastest firmware.