“Error loading RadChart Image” on IIS7

Question

I'm using a Telerik RadChart control on my ASP.NET web application.

This works fine when running on localhost, but now the application has been deployed to IIS7 and the following error appears:

Why is this? And how can I resolve the issue?

I've seen on some forum posts that the solution is to add the following into <system.webServer> in the web.config:

<add name="ChartImage_axd" path="ChartImage.axd" type="Telerik.Web.UI.ChartHttpHandler" verb="*" preCondition="integratedMode,runtimeVersionv2.0"/>

However, I have already done this, and the error is still appearing.