IIS7 deployment - duplicate 'system.web.extensions/scripting/scriptResourceHandler' section

Question

On attempting to deploy a .net 3.5 website on the default app pool in IIS7 having the framework section set to 4.0, I get the following error.

There i

Answer 1

Apparently, other have (had) this problem. They rebuild in Framework 4.0. Can you?

Also, see this about making sure your IIS is fresh.