i know that 1000 is too much. in my desperation, i was trying some crazy values.
i set the force to 10 to see whats going on. the bomb flys like a rocket to the sky...okay maybe i misunderstand the "VECTOR*vPos" part.
so i replaced "bomb_pos" with "nullvector". and now it seems that the bomb is hit by an explosion an flys to a random direction. but the box is still uneffected...even by a radius with 2000!