If your web site is running under IIS7 Integrated mode, the web server searches the HttpHandler registrations under the <system.webServer>
section of web.config. In this case you should register the HttpHandlers as shown in the help article Registering the HttpHandlers on Windows Vista IIS 7 Integrated mode
If you are still having problems after trying the suggestion above, please send your web.config, a live URL to your page so that I can examine the issue locally.
the Telerik team
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