Having a RadCombobox on a form and assign a EmptyMessage later containing a diacritical character, the EmptyMessage is treated like it has been entered as a value.
So it will make a call to the webservice using that value which it should not do.

Code example:
        protected void TestLinkButton_Click(object sender, EventArgs e)
        {
            this.CountryComboBoxControl.EmptyMessage = "Bitte wählen Sie ein Land*";
        }