Custom Server Control Error: Unable to get value of the property 'tagName': object is null or undefined

Hi Guys,
I am working with visual studio 2010 express, created a new web application, and started building a simple website. I started by creating my ownMenu Server Control by inheriting from the asp.net Menu class and overriding the render method.
All is well, when i view the site in debug mode, i recieve this annoying error:
Unable to get value of the property 'tagName': object is null or undefined
This error appears before the page load and seems to be a Microsoft JScript error.
This is how i am referencing the control in the web.config
<controls> <add tagPrefix="Controls" namespace="MyWebApplication.Controls" assembly="MyWebApplication" /> </controls> If i choose to continue the script error the page renders the navigation as expected.
 
Thanks.
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