AJAX.BeginForm PostURL being corrupted
The problem was using "action" for the name attribute on the submit buttons. As soon as I changed the name attribute to a different value, everything started working perfectly.
I'm guessing that there is a jQuery selector in the unobtrusive ajax library that got confused.
Do you have unobtrusive JavaScript on or off in your web.config? Im first guessing here the ms Ajax library is acting goofy so enable unobtrusive so we get jquery support.
What is your form action set to? Post your form HTML element if you can .