I do not see any Script manager in the attached mark-up screenshot - can you verify you have such added to the page?
Can you share the folder structure of your application with us? Is the BbcDocStore
folder placed inside the root folder of your application? I am attaching a very simple project to this reply demonstrating the file Structure RadFileExplorer expects with such configuration (you will need to add the Telerik Dlls to the bin folder of the site). Are you experiencing the same problem with it?
Telerik by Progress