"value cannot be null parameter name: key"

Try closing the Visual Studio and and access the same page. It should work. I also faced the same exception. If you see the exception it points to PageInspector of Visual studio which causing the issue. Not sure why VS is messing with application loading.

I tried everything you said and it didnt work. However, I found a workaround that, for some reason I dont know, worked. I added this to my web.config file:

 <add key="PageInspector:ServerCodeMappingSupport" value="Disabled" />

And it worked for me :D

This can be caused by browserlink in Visual Studio being enabled. Disable it:

http://www.asp.net/visual-studio/overview/2013/using-browser-link#disabling