Ok, Today i had this error with one of our client servers, now this is a new install then immediately patched to Update Rollup 12.
When trying to run any report you get the error:
"The base class includes the field 'reportViewer', but its type (Microsoft.Reporting.WebForms.ReportViewer) is not compatible with the type of control (Microsoft.Reporting.WebForms.ReportViewer)."
Screenshot:
So after a bit of research found that the Report Webviewer was updated from 2005 to 2008, but if the web.config has been modified the rollup doesn't upgrade the web.config file, well now this is strange as this was a fresh install and a straight upgrade.........
well after a bit of digging around the update files i found the entries that needed to be updated(see below), so updated these and voila!!!
Please change the entries in your web.config at the root of your CRM site
Under the HttpHandlers Section find:
Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
And replace with:
Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
Under the Assemblies Section find:
Microsoft.ReportViewer.WebForms, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
And replace with:
Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
Hope this helps others.
Phil