did you replace Telerik.dll in bin folder? if no, please replace by the one from DNN install package, if yes, check the binding redirect statements in your web.config, which may point to a specific dll version.

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Cheers from Germany,
Sebastian Leupold

   

Speed up your DNN Websites with TurboDNN

When you're in this position, you've got a serious error in your site.

The first thing to try is restoring the site to the state is was in before copying the file - hopefully you still have the original one?

The next place to try and look (if you can) is in the server event log. There might be an exception listed in there.

You can also look directly at the eventLog database table if you can get a direct sql connection. You'll have to sort by the date/time to see the latest error, and copy/paste the details into something like notepad to be able to ascertain what the error is actually saying.

Finally, you should try a complete application restart. Restart IIS if you can, or else at the very least 'touch' your web.config file to try and see if that helps.