When you start typing, the dropdown appears and then you leave the AutoCompleteBox without clicking, the cursor is not changing back to arrow.

As a workaround of the issue you could manually release the mouse capture in the Populated event handler of the control as shown below:


 private void AutoCompleteBox_Populated(object sender, System.EventArgs e)
        {
            if (Mouse.Captured is RadAutoCompleteBox)
            {
                (sender as RadAutoCompleteBox).ReleaseMouseCapture();
            }
        }