Looking at the code, it seems to be a problem with the redirect URL handling of authorize.net in AIM mode.
Could you change the code:
if(!empty($method->payment_params->return_url)){
$return_url = $method->payment_params->return_url;
}
to:
global $Itemid;
$url_itemid='';
if(!empty($Itemid)){
$url_itemid='&Itemid='.$Itemid;
}
$return_url = HIKASHOP_LIVE.'index.php?option=com_hikashop&ctrl=checkout&task=after_end&order_id='.$order->order_id.$url_itemid;
in the file plugins/hikashoppayment/authorize.php and try again ?