You are correct. Removing the reference to the Silverlight part, leaving the wrapper unchanged, meaning not adding the code you mentioned in your last reply, gives me the same error.
Googling, I found this thread here. Following up on that information, searching the sample apps folder installed under My Documents, I found the correct registration line for the CoreHandler, which should be:
<add verb="*" path="*.ashx" type="GrapeCity.ActiveAnalysis.Web.CoreHandler, GrapeCity.ActiveAnalysis.Web"/>
In addition, I noticed that both of the GrapeCity references in the project were set to Copy Local = False. Changing that to True, I get a Voila ! I get the control up in the browser without any errors.
Hope this helps,