AJAX :: Conctrol Toolkit HTMLEditor Slows Down Other Events On Page

I've made a test page, a HTMLEditor in a updatepanel. And a updatepanel with 1 butten and 1 textfield. If i press the button btnTextBox the _click code below is runned:

public partial class test : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnTextBox_Click(object sender, EventArgs e)
{
txtTextbox.Text = "Hellow world!";
}
}

It takes a few seconds bevore the "Hellow world" is in the texteditor. But if i remove the HTML editor, it going very quick! So if i add the ajaxcontroltoolkit in the page it slows down quite easy changes with some seconds.... so you get a very slow working page. How can i speed this up. The test ASPX page:

[Code]....