Problem with System.Web.Configuration.ScriptingProfileServiceSection
I was working on a project that was upgraded from ASP.Net 2.0 to ASP.Net 3.5. I had no problems running the project until I added the latest version of Telerik controls to the project. Just for your information, I'm a HUGE fan of Telerik controls. If you are a ASP.net developer you should try them.
After I added the controls I got the following error: Unable to cast object of type
'System.Web.Configuration.ScriptingProfileServiceSection' to type
After search around it turns out that you need to remove xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0" from you web.config. This is left over from visual studio upgrading the project.
Now it is working again.