Please run the sample project and enter some tokens. Then, hit Backspace and the following error occurs:

System.ArgumentOutOfRangeException: startIndex cannot be larger than length of string.
Parameter name: startIndex
   at System.String.Substring(Int32 startIndex, Int32 length)
   at Telerik.WinControls.UI.TextBoxViewElement.ReplaceTextBlock(ITextBlock targetBlock, Int32 startCharPosition, Int32 endCharPosition, String text)
   at Telerik.WinControls.UI.TextBoxViewElement.ReplaceTextRange(ITextBlock targetBlock, Int32 startCharPosition, Int32 endCharPosition, String text)
   at Telerik.WinControls.UI.AutoCompleteBoxViewElement.ReplaceTextRange(ITextBlock targetBlock, Int32 startCharPosition, Int32 endCharPosition, String text)
   at Telerik.WinControls.UI.TextBoxViewElement.ReplaceOverride(TextPosition startPosition, TextPosition endPosition, String text)
   at Telerik.WinControls.UI.AutoCompleteBoxViewElement.ReplaceOverride(TextPosition startPosition, TextPosition endPosition, String text)
   at Telerik.WinControls.UI.TextBoxViewElement.Replace(TextPosition startPosition, TextPosition endPosition, String text)
   at Telerik.WinControls.UI.RadTextBoxControlElement.Delete(Boolean nextCharacter, Boolean isControlPressed)
   at Telerik.WinControls.UI.TextBoxInputHandler.ProcessDelete(Boolean moveNext, Boolean isControlPressed)
   at Telerik.WinControls.UI.TextBoxInputHandler.ProcessKeyDown(KeyEventArgs e)
   at Telerik.WinControls.UI.RadTextBoxControlElement.OnKeyDown(KeyEventArgs e)
   at Telerik.WinControls.RadItem.DoKeyDown(KeyEventArgs e)
   at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
   at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
   at Telerik.WinControls.RadItem.RaiseKeyDown(KeyEventArgs e)
   at Telerik.WinControls.ComponentInputBehavior.OnKeyDown(KeyEventArgs e)
   at Telerik.WinControls.RadControl.OnKeyDown(KeyEventArgs e)
   at System.Windows.Forms.Control.ProcessKeyEventArgs(Message& m)
   at System.Windows.Forms.Control.ProcessKeyMessage(Message& m)
   at System.Windows.Forms.Control.WmKeyChar(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at Telerik.WinControls.RadControl.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)