The Paypal Return link is not working for me.

•just upgraded from Smith Cart 3.2 to Smith Cart 4.58
•also recently upgraded to DNN 5.06.03 (45).
•testing on chrome and IE 8.
•paypal business account set up. Auto Return set to ON
•Buynow module: authorize.net primary gateway and checked Paypal option as well.
•IIS Manager - SSL configured for port 443
When I make a purchase (live purchase, using personal paypal account), everything works smoothly, except the Return link.

The paypal return/confirmation page offers a link back to the site, if it doesn't redirect in 10 seconds, but it does nothing.

Looking at the page source on the paypal site, I see this:

<form method="post" id="merchantErrorForm" name="merchantErrorForm" action="https://www.smarthf.com:443https://ww..." class="">

Reference Thread  - http://www.smith-consulting.com/Forum...

So, perhaps this is a firewall issue. I just need to know exactly what needs to be done, to communicate with our web host.

Thank you. 2 quick questions: I don't see the upgrade file under Downloads (or rather I get "you don't have access"). And second, is doing this upgrading easier than a full upgrade (ie backing up db and files, deleting stored procedures & tables & files, installing, etc.)?

Thanks again.