ASP.NET Form Fields Not POSTing from colorbox

I’ve got a form that is displayed inside a jQuery colorbox. When the form is submitted, the fields within that form are not being posted back to the page. I modified the javascript to store the form fields into hidden fields on a submit and those DO post back. The problem is, since this is a login box, I really don’t want to move the password around like that. The main form content is inside an update panel. Here is the code for my master page: