A hang-up problem with S2 mobile is the most common problem one faces. And, when it does your heart literally comes to a halt. First most do not panic because you will not lose your device.
You just need to follow this little advice and your SGS2 will be back in action.
First try switching your device by pressing the POWER ON button for few seconds.
In case this does not work then Follow this combination: VOLUME UP + HOME BUTTON + POWER buttons simultaneously.
Your screen will come back enjoy 🙂
NOTE – No data will be lost if you follow this method.