what could cause zen cart to hang at chekout?

I am getting customers reporting that they cannot progress from step 2 of the checkout. They add the item to their cart and get the shipping method screen but then it will not progress to the payment screen, it just hangs on the same page. It will go back but not foreward in the chekout process.

The puzzling this is that I have put through several successful test orders so it seems to work for me and our webhost tech did not see a problem either.

So what could be causing this?

(and I know for a fact it is NOT user error or problems with the customer's computers because one of our staff was able to replicate the fault as well and I was able to see the fault myself once, so it seems to be an intermittant issue somehow).

Many Thanks,
Trillian

what do you have setup for shipping?

I am using the zone shipping module.

But as I say, I was able to duplicate the error myself using my own customer account. And now I was able to make several successful test orders. I have not changed anything with the shipping or payment modules.

A customer just informed me that this was happening on one of the three carts I have on one VPS. I'm guessing the problem is with the VPS; but, I don't know where to look. I also wonder if it could be the connection to USPS?

I'm running fully patched Zen 1.3.8. I'm on a CentOS box with cPanel.

What does "hang" mean? Does it mean you're getting a blank page? Or an error message? or what? https://www.zen-cart.com/tutorials/index.php?article=82
Can you replicate the problem? Have you tried? What *exactly* is happening that's undesired?

I found the answer in a misconfigured iptable-based firewall script.

By hanging, I meant the progress bar spun until it quit trying and reloaded the page, with a small message (the fault of my css), indicating it couldn't receive a quote from usps.com.

In another life, when I was young and skinny, I was a professional classical ballet dancer. I was known to be able to quickly and efficiently solve the inevitable crises that happen during a live performance, without losing my head or missing a beat. Now that I'm teaching and doing this computer thing, a client has a problem and I start pulling my hair out and otherwise freaking out. It's fairly embarrassing.

Maybe others reading this will use me as an example and take a few breaths, calm down, and read everything on the screen.
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