When using Authentication with a Web Application you might get Sys is undefined when starting up in Visual Studio using IE. This is an Authentication issue that is resolved by using this solution.

source: http://blogs.telerik.com/blogs/posts/10-03-16/common-reasons-for-the-lsquo-sys-is-undefined-rsquo-error-in-asp-net-ajax-applications.aspx

 <location path="Telerik.Web.UI.WebResource.axd">
 <system.web>
 <authorization>
 <allow users="*"/>
 </authorization>
 </system.web>
 </location>

Hope this helps someone out there!