ASP.NET Response.Redirect with jQuery Mobile - Url hashing

I have a standard forms auth ASP.NET application. My Registration and Login page are in the same .aspx file with 2 jQuery Mobile pages. If I postback my ASP.NET page, such as the user fails to login correctly...etc The Url hash starts appending to itself over and over.

Example Url:
http://localhost:56644/Register.aspx?ReturnUrl=%2fDefault.aspx%3fbla%3dtest&bla=test#Register.aspx?ReturnUrl=%2fDefault.aspx%3fbla%3dtest&bla=test

Once my user is authenticated I want to Redirect to the ReturnUrl without all the hash information or find a way for the url to remain during postbacks?

Markup:

<div data-role="page" id="register">
    <div data-role="content" data-scroll="true" data-theme="b" class="Content">
        ......  
        <a href='#login'>Login</a               
    </div>
</div>
<div data-role="page" id="login">
    <div data-role="content" data-scroll="true" data-theme="b" class="Content">
        .....                             
        <a href='#register' >Registered Yet?</a>
    </div>
</div>

Code-behind on Register.aspx:

protected void btnLogin_Click(object sender, EventArgs e)
{        
    if (LoggedIn)
    {
        FormsAuthentication.SetAuthCookie("blabla", true); 
        //Note: Request.QueryString["ReturnUrl"] = "/Default.aspx?bla=test";
        Response.Redirect(Request.QueryString["ReturnUrl"]);

    }
}