USPS has come out with new coding for API calls, which is what Zen Cart uses to retrieve shipping quotes. This new API coding will start being used on 9/7/14.

Quote from the USPS website: "The Web Tools APIs will be moving to a new platform where data validations will more closely adhere to the published technical specifications. In some cases, improperly formatted XML values that are accepted currently will result in error responses on 9/7. While we have taken steps to make this transition backwards compatible, we strongly recommend testing your API integrations to avoid issues on 9/7."

Linda, one of the Zen Cart developers, just released the new update a few hours ago if you are able to install the module yourself.

If you use USPS as a shipping module, it needs to be updated. If you need us to install the update, I will be working tomorrow to get any one who orders it from our website here. As usual, installs are done in the order they are received.

Also very important... when you check out - PLEASE click on the graphic on the checkout success page that says to go to a secure form to input your information so we can access your server and your admin. Once to our data collection site, please click on Module Installation. It is important that you enter the correct info, so as to not delay things.