I'm still having issues. All four of these particular sites are hosted with Godaddy. It appears that when I set up the hosting on the original site (about 3 years) plesk defaulted to "Medium" trust. Which I didn't notice and didn't cause any issues with DNN or the modules used on the site. Then I setup the other 3 over the next year or so, and it appears plesk defaulted to "Full" trust. Those sites installed the hotfix without issue, but the older one running in Medium Trust gave me the error when accessing the patch Telerik component.
I tried just setting the hosting space to "Full Trust" via the ASP.NET section of plesk, which does add the code fragment you mention to the web.config file. But, when starting the site I quickly get a server side error "The connection name 'SiteSqlServer' was not found in the applications configuration or the connection string is empty."
My guess is that since the site was built and maintained over the years as a Medium Trust environment that something in the web.config hasn't been configured correctly for Full Trust. In fact, although all four sites are running basically the same framework, the working web.config files are almost 80 lines longer than the one that throws the error. So quite a bit of difference.
I did find one section that might be relevant. The working web.config files have a section commented as "<!-- Connection String for SQL Server 2005 Express -->" with an add name command starting with "add name="SiteSqlServer" connectionString="Server=" and containing the server ID, database ID and password".
This particular section isn't in the web.config that is set for Medium Trust.
I might try adding the missing section to the problematic web.config file after getting a full backup of the site and database.
Thanks and BTW - I did get your PM, but my reply bounced.