So I was working with Zen-Cart 1.3.8a which has Google Checkout integrated – And noticed that users were not able to sign into their accounts (users would get an error like “There was a security error when trying to login”). This is because the new version of Zen-Cart uses a new security token which Google Checkout does not recognize. The fix that I made was taking the references to Google Checkout out of the /templates/YOUR_TEMPLATE/templates/tpl_login_default.php (or /templates/classic/templates/tpl_login_default.php) file(s).
You can take out these references manually:
// ** GOOGLE CHECKOUT **
include(DIR_WS_MODULES . 'show_google_components.php');
// ** END GOOGLE CHECKOUT **
Or if you haven’t made any modifications to that file, you can copy the code from the original file located in the Zen-Cart download (just make sure you backup any files you modify!)
If you have any problems or need help with Zen-Cart, visit www.ZenCartPros.com