Screen not responding

Apologize if this has been covered in any threads before, searched but could not find anything.

Phone:
Iphone 3G, OS 3.0, not jailbroken, not stolen. Have up until today never had a problem with it (bought it december 08).

What happened:
Earlier today my wife tried to call me. It showed up on the screen and i slid the answer arrow to the right as usuall.
For some reason though it was stuck. Phone kept ringing but nada happened.
I then held down the sleep button to restart it, only for the whole thing to hang itself. The shut off button is still there but seems i can't effect it.
The home, sleep and sound buttons all still seem to work.

Is there a hard reboot possibility or what need i do?

 

Nice, managed to restart it after some work and the screen is now working again.