The AJAX isn't working when I request site via the DomenName

Question

Hi All!
Probably it is a stupid problem, but I have it.

I have a site on ASP.Net 3.5 C#. It is all right if load it by path like this //000.000.00.00/Site/Default.aspx in one word request to the site via the server IP.
But I have the DN, all that come on it redirecting on //000.000.00.00/Site/.

And here are problems:

C# code
Response.Redirect("Form.aspx");

or
Code C#
Response.Redirect("~Form.aspx");

Making the DomenName/Site/Form in browser's URL when must be ONLY DomenName/Form

Code C#
Response.Redirect("/Form.aspx");

Gives the desired result but in this case site don't working via the server IP.
BUT it is only half of problems.

Main problem is:
Because of this troubles with references the browser throw the exception:
"ASP.NET Ajax client-side framework filed to load".
What I can do with this??
The all of web.config settings I already have checked there are all right.

Thank you everybody, who answer me.

P.S. Sorry for my english.