I am using ZenCart 1.2.6d. I recently cloned the flat rate shipping module which seems to have gone weill, but now I am having problems with the checkout process.

My shipping methods show up on Step 1 of the checkout, but when I click continue, I am led to a blank page. If I type in the URL for the checkout_payment page, my shipping selection has been successfully stored. I can then continue to step 3, but when I click continue on that page, I am led to another blank page. The order processes and I receive a confirmation email.

It appears that something is causing the zen_redirect function to fail, but I cannot tell what that is.