The only known reason for such error is incorrectly registered http handler. Does the issue appear in a brand new web site with a single page with RadChart in it? Did you try to register the http handler from the chart smart tag as shown here
? You you still experience the same problem, can you send this web-site to us, so we can review it? Thanks.
Note, that the property is UseSession
. Still, this does not seem to be relevant in this case, as the property remains with its default value - true
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