Sorry for the late answer but when I received/read your answer it was quite in the night.

When you've such problems reinstall AJAX with it's MS extensions - wasn't that the installation it will not make more harm. 
So far I know a DNN 4.4.4 doesn't/didn't exit - I asume your using 4.5.4.

I could talk a lot about DNN and AJAX but after my point of view the most relevent aspect is: DNN is not built around AJAX but rather utilizes this technology in many ways. I don't know in detail in what extend the core library uses AJAX but for over 2 years AJAX is integrated in the ClientAPI.  When you're using the DNN ClientAPI 4.5.4+ you must install the MS AJAX Extensions too. (look: http://www.dotnetnuke.com/Community/Blogs/tabid/825/EntryID/1463/Default.aspx) 

A very helpful example for a DNN AJAX Module can you find it from Telerik (RadControls_Q2_2007_DNN_trial(2007_10_04).zip; look http://www.telerik.com/products/dnn/download-trial.aspx). 

I hope it's a little help for you to solve your problem

Hi Michael and Jascht,

Ok, the problem in the code view.ascx.cs is that a DLL is missing with namespace: DotNetNuke.Framework.AJAX.

      protected void Page_Load(object sender, EventArgs e)
        {
            try
            {
                if (DotNetNuke.Framework.AJAX.IsInstalled())
                {
                    DotNetNuke.Framework.AJAX.RegisterScriptManager();
                }

Seems there is more than the System.Web.Extensions DLL and the AjaxControlToolkit.dll ?

So, I  finally give up and am downloading  DNN 4.6.2 upgrade and install versions right now.

I will try the upgrade first.

Peace, LA Guy