I created a block which I don't really need. I tried to delete it, but it says it can't be deleted because it's in use. I checked all layouts and I don't see any reference to this block. When it tried to turn it off, it says it's NOT in use. I don't understand the contradiction or why I cannot delete it.

yes. cookie for domain cover all subdomains

Sorry, your answer is not clear. I asked if the proposed solutions are mutually exclusive or two steps for the same solution. You gave me a yes answer. Yes to what? Please clarify. How can I keep the subdomains and get rid of the Ajax error? What happens if I add "hardcoded" domain into cookie set? Will it get rid of all subdomains? That's not clear to me. I appreciate an answer all my questions. I don't want to implement anything unless I know for sure what I'm doing. Thank you.

you have issue with cookies. Abantecart set cookie for your domain, but you created a lot of subdomain such as ru. fr. es. etc that have it's own cookie scope

How can I get his resolved?

I went to localization and selected Turkish. Under "Load missing language data" I typed in "English" as the source language, then clicked "Load". Then I cleared my cache files both in Abantecart and my browser. I tested a page in Turkish, but I keep getting the same error.

I'm getting an "Unknown Ajax Error" when adding to cart from this category page in French: http://fr.assistech.com/store/magnifiers (Fr. "ajouter au panier" for adding to cart)

I tried the workaround provided by Abolabo at http://forum.abantecart.com/index.php/topic,2473.0.html , but it did not work for me.

I noticed this problem only happens when I'm in a language subdomain such as "fr" for French or "es" for Español. If I switch to English --> http://assistech.com/store/magnifiers , the error is gone. However, if I select English from the language dropdown menu, it adds an "en" prefix to the URL, therefore causing the same error.

Please note: I'm not using the built-in translator that comes with Abantecart. I use a third-party solution that requires adding a language prefix to the URL.

I appreciate if anybody could tell me what needs to be done to fix this error. Thank you!

Thank you, Lee. I visited mysqlreports.com. Is Smart Report Maker what I need? Do you know if it's easy to use?
 

Handling Fee? http://www.abantecart.com/ecommerce-documentation/48-admin-user-manual/extensions-menu/order-totals#Handling%20Fee

I don't mean a handling fee. I mean a shipping overcharge for certain items only.

Ollie,  I believe there may be an issue with the extension, as of Sept 7,  the UPSP has a new API.  I have posted to the Admins regarding seeing if the extension needs some update.  You can see at this link.
http://forum.abantecart.com/index.php/topic,2673.msg11406.html#msg11406

Thank you, Lee. I followed this link and the instructions on that page and everything is working well now.