MVC4 Ajax.BeginForm not replacing UpdateTargetId
There is a problem with jquery.unobtrusive-ajax.min and JQuery 1.9 because JQuery 1.9 doesn't support the live() method any more. So you should use the JQuery migrate plug-in, and reference the JQuery migrate js.
Make sure you include the unobtrusive-ajax.js to the page, which you have placed your ajax form.
<script src="~/Scripts/jquery.unobtrusive-ajax.js"></script>
I had this problem, I just installed the latest unobtrusive package from NuGet and solved the problem
PM> Install-Package Microsoft.jQuery.Unobtrusive.Ajax
Will need JQ 1.8+