There is a duplicate 'system.web.extensions/scripting/scriptResour

estou com esse erro :

There is a duplicate 'system.web.extensions/scripting/scriptResourceHandler' section defined

Print :

/applications/core/interface/imageproxy/imageproxy.php?img=http://i.imgur.com/10CeqbY.png&key=636f7c66b07bb2780a38f9bac138803a5215d393a5d8e7015f010b59e66d3d8b" alt="10CeqbY.png" />

Web.config : http://pastebin.com/VSG6KvZ2

estou com esse erro "500.19"