Using Visual Studio and Asp.Net 3.5 created an Asp.Net application using the SSRS 2005 Microsoft.ReportViewer.WebForms version 8.0.0.0 control.

Trying to print a report directly from http://ServerName/Reports using the little printer button worked fine, the cab was downloaded correctly and installed.  However using the printer button on the custom Asp.Net application resulted in the error "Unable to load client print control.":-

Strange, I checked the Asp.Net web.config and the correct assembly declarations where made:-

<add assembly="Microsoft.ReportViewer.WebForms, Version=8.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />

Saw lots of posts about installing the following on the server:-

Microsoft Report Viewer Redistributable 2005 

Microsoft Report Viewer Redistributable 2005 Service Pack 1 

Report Viewer Redistributable 2005 Service Pack 1 GDIPLUS.DLL Security Update 

So did this but still the error persisted.

Fix:-

On the server, open "Internet Information Services (IIS) Manager

Open up "Sites" and where you website is located on this I am just using "Default Web Site":-

Then click "Handler Mappings":-

Then click "Add Managed Handler...":-

Under Request Path add:-

Reserved.ReportViewerWebControl.axd

Under Type add:-

Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a

Under Name Add:-

Reserved.ReportViewerWebControl.axd

So should look like:-

Click OK and restart IIS.

Now you Asp.Net application print button from the Report Viewer control should work.