SQL Reporting :: AllowPartiallyTrustedCallersAttribute Or RSClientController Undefined - Error "Type Microsoft.Reporting.RdlBuildProvider Cannot Be Instantiated Under A Partially Trusted Security Policy"

first of all: this probelm was already an issue in [URL] but it does not resolve my problem: I have VS2008 and SQL Server 2008 Express with Adv. Option istalled. When compiling a page with the reportviewer control I get the error Type 'Microsoft.Reporting.RdlBuildProvider' cannot be instantiated under a partially trusted security policy (AllowPartiallyTrustedCallersAttribute is not present on the target assembly). C:websitesadAgencyweb.config

From the obove mentioned post I learned to use <trust level="Full" /> in the web.config file (which I never used on other Implementations that work). Now the compilation works, but when I start the web application and call that page I get a lot of JScrip Errors like: Runtime error in Microsoft JScript: 'RSClientController' is undefined, which comes from a line in the dynamic page.aspx file: document.getElementById('ctl00_maincontent_ReportViewer1').ClientController = new RSClientController "ctl00_maincontent_ReportViewer1_ctl03", "ReportFramectl00_maincontent_ReportViewer1", ...

I should mention, that I had SQL Server 2005 Express uninstalled before the 2008 version.