Script pausing unexpectedly in collision

I have this snippet of code:

collision(integer total_number)
{
agent = llDetectedKey(0);
llPushObject(agent, 1.0*llRot2Fwd(llGetRot()), ZERO_VECTOR, FALSE); //Move the avatar forward a bit.


But llPushObect won't start until you move your avatar with your arrow keys. Then the rest of the script kicks in. It seems the collision is not being detected, even though the avatar is standing on top of the object the script is running from.

Any suggestions on how to stop this pause?

Try collision_start rather than just plain collision.