When installing the SUPEE-7405 on magento 126.96.36.199 the patch is trying to remove the comment on these lines:
-/* @var $_helper Mage_Authorizenet_Helper_Data */
-$_helper = $this->helper('authorizenet');
+/* @var $_helper Mage_Authorizenet_Helper_Admin */
+$_helper = $this->helper('authorizenet/admin');
However the comment
@var $_helper Mage_Authorizenet_Helper_Data
was not added until magento 188.8.131.52 and not in 184.108.40.206
I have got around the issue by added the comment to the file and then running the patch.
Hi @rob3000, were you able to get this working?
I needed to add
/* @var $_helper Mage_Authorizenet_Helper_Data */
above the helper declaration comment to the file and then ran the patch again and it worked.