In some old versions of Telerik Open Access you may come to this exception.I am not quite sure about the latest versions.
However, I've found a forum post that explains that this exception occurs if your project wasn't yet enabled for Open Access.
This wasn't my case so I tried some other things.
At the end, it appeared that "The assembly 'xxx' does not have a config file with an openaccess node" exception may occur if your app.config file is broken. It should be a valid XML file. In my case I have forgotten to close a <class> node with its corresponding </class> ...
Edit: As Yosif Yosifov stated, there is an easier way to check if your app.config file is fine. Simply select Telerik -> Open Access -> Configuration -> Check Settings ... dialog from Visual Studio menu.
