If you're using Magento version 18.104.22.168, you're affected by the July 28 changes of the Unites States Postal Service that affect Priority Mail and Express Mail Shipping options. When you try to connect your Magento store to the USPS production server you get the error: “This shipping method is currently unavailable. If you would like to ship using this shipping method, please contact us”, or, depending on what shipping options you have selected in the shipping configuration, you may only see Media Mail and Library Mail. Usually what this means is that you need to install a Magento patch PATCH_SUPEE-1868_CE_22.214.171.124_v1.sh in order to fix the USPS shipping options.
My provider doesn't allow ssh shell access to my shared server unfortunately so my first attempt at installing the patch was resorting to writing a short perl script to run the patch shell file. No dice, no matter what I did I couldn't get the thing to do it's magic. Apparently my provider has the machine so locked down there is no way for me to run the patch and they refused to run it, even though I provided a link to the official patch and explained that it only affects my instance of the software and they can read the script in clear text. No way to convince them to do it. It's a security problem they say. Oooooooooooo-K fair enough.
So I get this bright idea, don't know if it's really going to work, but I decided to install a Ubuntu Linux virtual machine on my local PC and install the exact same Magento version. Once it's up and running, I applied the patch to my virtual machine's copy of Magento. The nice things is when the patch is done, the file app/etc/applied.patches.list contains the list of files you need to do the patch by hand. I copied the files off the virtual machine onto my production store and the USPS shipping options were there. Here is a list of the files I had to copy:
patching file app/code/core/Mage/Paypal/Model/Express/Checkout.php
patching file app/code/core/Mage/Usa/Helper/Data.php
patching file app/code/core/Mage/Usa/Model/Shipping/Carrier/Usps.php
patching file app/code/core/Mage/Usa/Model/Shipping/Carrier/Usps/Source/Method.php
patching file app/code/core/Mage/Usa/etc/config.xml
patching file app/code/core/Mage/Usa/sql/usa_setup/upgrade-126.96.36.199.1.1-188.8.131.52.1.2.php
patching file app/etc/applied.patches.list