This is a general error which does not fully describe the problem. Can you tell us when did you start to get the message - immediately after the upgrade? Do you have custom controls on your website? Some of them might be breaking the index but indeed it is strange if it has worked before.
What you need is to escape the crawler request. Please refer to the following code sample:
if (this.Page.Items["IsInIndexMode"] == null)
// your logic here.
Also can you try and login to your website and replicate the issue - then attach the trace log
and send it to me so I can have a closer look at the service exceptions.
the Telerik team
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