The Dink Network

Look in en-pill1 for the braincheck, which is this:
if (get_sprite_with_this_brain(9, &current_sprite) == 0)
{
//no more brain 9 monsters here, lets unlock the screen
screenlock(0);
playsound(43, 22050,0,0,0);
}
in the die procedure.

It isn't seeing the sprite it's attached to because the second bit tells it a sprite to ignore - get_sprite_with_this_brain(9, <ignore this one> );

Edit: Your enemies are brain 9, right?
If the sprite with the script is out of the way somewhere, try sp_nodraw() instead of sp_active().