Hi Anton,
We are not able to diagnose the issue from the exception alone. We need to see the issue first-hand so we can study and learn what is causing it. Is your application publicly accessible? If not, can you provide a sample site that demonstrates the issue you are experiencing?
As an alternative you can record and send us a Fiddler trace using
FiddlerCap, which is a good substitute for direct access. Basically with that trace we'll be able to "simulate" your app in order to reproduce the problem. If you feel that this information is sensitive, you can submit a support ticket which is confidential, unlike this forum. Thank you for providing the information we need to best assist you.
Regards,
Plamen
the Telerik team