change the script to:
<SCRIPT LANGUAGE="JavaScript">
// <!--
function shipsame(form){
if(form.sameasbilling.checked){
form.address.value = form.second_address.value;
form.address2.value = form.second_address2.value;
form.city.value = form.second_city.value;
form.state.value = form.second_state.value;
form.zip.value = form.second_zip.value;
}
}
else{
form.address.value = "";
form.address2.value = "";
form.city.value = "";
form.state.value = "";
form.zip.value = "";
}
//-->
</script>