Problems with Checkout when using Paypal and Cheques/Money Orders

I have two sites both running v511.

https://www.elvisstuff.co.uk
https://www.moviepostersuk.com

The first site is running fine with no problems at all. The second site https://www.moviepostersuk.com I've just set up using the same settings as the first and I'm encountering problems with the checkout.

Main main issue occurs when paying with Paypal. The process runs fine. The payment goes through to my Paypal account as normal. Emails are issued as normal but the item remains in the shopping cart and doesn't show up as an order in my Admin section. Any ideas how to rectify this?

The second, minor problem, is when paying by Cheque/Money Order everything works perfectly until I try to delete the order and restock the item back to inventory. I can delete the order without problem but the item is not restocked. This is a niggly issue rather than anything major as I can restock manually but it would be nice to have it working as it should.

As a sidenote both sites are running from the same IP address and I know that SSL requires different IP addresses but as I'm not using SSL I didn't think it would be an issue. I'm assuming this has nothing to do with the problems I'm encountering but thought it might be worth mentioning.

Any help would be appreciated as I think I've almost got my second site up and ready for launch.

Start with a list of all and any mods or changes you've made to your store from the default package.

The only mods I've done is installed the Dragon and Antiquity templates and installed the Telephone Not Required On Signup mod. The latter I also installed on my first site with no issues. I've also changed the spelling of check to cheque and changed the weights from lbs to kgs. Again I did these changes to the first site without any issues.

Which PayPal module are you using?
If you're using Standard, remove it and use Express Checkout instead.

Also, see http://www.zen-cart.com/content.php?124-blank-page and study the errors in your log files along with the FAQs search: http://www.zen-cart.com/search.php?search_type=1#ads=24&

Thanks DrByte
I've done as you suggested [and moved well out of my comfort zone in the process] but it's worked a treat. Many thanks for helping me out.

I'm still having trouble with the money order option though. It is now restocking the items but if the original order took the last item and switched off the item from the inventory the restock does not switch it back on again [I'm talking about the red and green button thingies] is this normal or do I need to do something the get it to switch back on?

Yes, normal. Simply go to the product and re-enable it. Either by clicking the red dot in the list of products, or by editing the product and changing the radio-button at the top.

Thanks DrByte, your help is much appreciated.