Please check with the app.config file with your application, the only delay might happen due to your config file, else there is nothing else to happen this kind of issue ...
Check if your config has been changes as per the change in framework
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
Also check with the necessary bindings reflected properly in your config. or just delete your existing config and create new (Delete and updated the web references again)