Desperately need some help - checkout broken

Hi
I've gone through a process today on a site currently running Zen Cart 1.3.7. I want to upgrade the whole site to the newest version and am in the process of doing that in the background, but my customer wanted the Lightbox and I found a version that runs on 1.3.7.1. So, today I added all the required patches to bring it to 1.3.7.1 and applied the Lightbox.

However, although it all looks fine, when you click on the Checkout button from the shopping basket, you get a blank page and a Server 500 error.

I'm unsure where to start looking at the cause of this because the file it's trying to display is main_page=checkout_shipping and I'm sure I haven't made any changes to the shipping templates.

If anyone could give me a steer on how to debug this I'd really appreciate it, it's either that or undo everything I've done today.

Thanks in advance

As you have added/edited some files look at both tutorials
https://www.zen-cart.com/tutorials/index.php?article=63
https://www.zen-cart.com/tutorials/index.php?article=82

Hey kobra

Thanks for the advice. I will definately have a look at those.

In the meantime, I seem to have found the source of the problem. One of the listed fixes for taking the cart to 1.3.7.1 came from thread http://www.zen-cart.com/forum/showthread.php?p=317535#post317535. The fix was the removal of a close bracket from a piece of code in the includes/classes/order.php. By putting the close bracket back in, the cart works fine.

I wasn't actually sure whether I needed to apply this fix, it seemed to be optional and referred to Money Orders, which we don't use. But I'd love to know why that broke the cart if you could throw any light on it?

Thanks again for taking the time to reply.

Code is too old and can not check as I have not had a 1.3.7 install for years

Fair enough kobra. As I say, it doesn't seem to be required and I'll be upgrading the whole site next month. Everything seems to be working OK now.

I'll definately familiarise myself with the contents of the two links you gave me though. Oddly, when I searched for server and 500, I didn't get anything back.

Thanks again for your time.