Please help a scripting noob.

Well this script refuzes to work right,If someones flying / driveing / running..it rezzs and stops them from hitting me,But if there walking...It dos nuthing at all!,Truly irrertatin,can someone please help with this?
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default
{
state_entry()
{
llListen(0,"",llGetOwner(),"";
}
listen(integer channel,string name,key id,string message)
{
if(message=="shield on"
{
state on;
}
}
}
state on
{
state_entry()
{
llSensorRepeat("","",AGENT|ACTIVE|PASSIVE|SCRIPTED,40,TWO_PI,0.1);
llSetTimerEvent(0.01);
llListen(0,"",llGetOwner(),"";
}
listen(integer channel,string name,key id,string message)
{
if(message=="shield off"
{
state default;
}
}
sensor(integer i)
{
integer i;
for(i=0;i<15;i++)
{
if(llVecDist(llGetPos(),llDetectedPos(i) + llVecNorm(llDetectedVel(i))) < llVecDist(llGetPos(),llDetectedPos(i)) && llVecMag(llDetectedVel(i)) > 5.0 && llDetectedKey(i)!=llGetOwnerKey(llGetOwner()))
{
rotation rot = llGetRot();
rotation drot = llDetectedRot(i);
rotation between = llGetRot() * llRotBetween(<0.5,0,0> * llGetRot(), llDetectedPos(i) - llGetPos());
llRezObject("shield",llGetPos() + <0.5,0,0> * between,ZERO_VECTOR,between,0);
}
}
}
}

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PS i am on the teen grid.

Take 'SCRIPTED' out of your sensor flags. SCRIPTED doesn't quite behave as you'd expect, and prevents a sensor from detecting avatars.

Also, you might want to change your sensor() event to:

sensor(integer num)
	{
		vector mypos ;
		vector targetpos ;
		vector targetvel ;
		
		integer i;
		for(i=0;i<num;i++)
		{
			mypos = llGetPos() ;
			targetpos = llDetectedPos(i) ;
			targetvel = llDetectedVel(i) ;
			
			if(llVecDist(mypos,targetpos + llVecNorm(targetvel)) < llVecDist(mypos,targetpos) && llVecMag(targetvel) > 5.0 && llDetectedKey(i)!=llGetOwnerKey(llGetOwner()))
			{
				rotation rot = llGetRot();
				rotation between = rot * llRotBetween(<0.5,0,0> * rot, targetpos - mypos);
				llRezObject("shield",mypos + <0.5,0,0> * between,ZERO_VECTOR,between,0);
			}
		}
	}

This way it will only cycle through the number of objects detected, and not always the full 16 objects it can detect, and will probably be a little more efficient since it's not making so many calls to llGetPos() and llDetectedPos().