MVC + Ajax call to Controller Loses Authentication

Question

I've seen similar issues in some posts but none of the answers have helped yet. My MVC app has a few AJAX/JSON response methods in one controller, and the calls get to destination but it doesn't work in IE or Chrome, and in mozilla it does, but Firebug returns a very strange set of 3 attempts (all return 401 error) but the last one does actually work!

My App has windows authentication, how can I extend this to my Ajax methods? the rest of the app works fine. I've tried bypassing the 401 by returning 200 Status from Global.asax (Application_EndRequest) but continues to do the same. Basically all of my Ajax methods have the same problem.

Here's an image from my firebug console.