I posted a link below to the updated module....
2 things you should understand..... My time for creating, lending support and just plain answering questions is donated by me.
Secondly, you read far enough down to find bug fixes... BUT failed to download the updated module from the link I posted.
The updated module has been submitted to the downloads section, but they are swamped ... Which is why I provided the link.
FYI also, there are some additional added instructions in the newest update... You are in fact 2 updates behind.
So... Download the module http://pro-webs.net/store/index.php?...products_id=96
and try again... or don't. Zen Carts by their very nature have a wide range of modules and customizations... The issue could be anything, but installing the latest version is a good start.
Additionally, are all of these sites with the same webhost? Have you checked if you can upload in this manner or know that you can?