To reproduce:
  public Form1()
        {
            InitializeComponent();

            PropertyStoreItem intItem = new PropertyStoreItem(typeof(int), "Integer", 1);
            PropertyStoreItem floatItem = new PropertyStoreItem(typeof(float), "Float", 1f, "Property storing a floating point value.");
            PropertyStoreItem stringItem = new PropertyStoreItem(typeof(string), "String", "telerik", "Property storing a string value", "Telerik");
            PropertyStoreItem dockItem = new PropertyStoreItem(typeof(DockStyle), "Dock", DockStyle.Top, "Property containing DockStyle value", "Layout", false);

            RadPropertyStore store = new RadPropertyStore();
            store.Add(intItem);
            store.Add(floatItem);
            store.Add(stringItem);
            store.Add(dockItem);

            this.radPropertyGrid1.SelectedObject = store;
        }

        private void radButton1_Click(object sender, EventArgs e)
        {
            PropertyStoreItem intItem = new PropertyStoreItem(typeof(int), "Integer111", 1);
            PropertyStoreItem floatItem = new PropertyStoreItem(typeof(float), "Float111", 1f, "Property storing a floating point value.111");
            PropertyStoreItem stringItem = new PropertyStoreItem(typeof(string), "String111", "telerik", "Property storing a string value", "Telerik111");
            PropertyStoreItem dockItem = new PropertyStoreItem(typeof(DockStyle), "Dock111", DockStyle.Top, "Property containing DockStyle value", "Layout111", false);

            RadPropertyStore store = new RadPropertyStore();
            store.Add(intItem);
            store.Add(floatItem);
            store.Add(stringItem);
            store.Add(dockItem);

            this.radPropertyGrid1.SelectedObject = store;

        }

WORKAOUND: 

radPropertyGrid1.PropertyGridElement.SplitElement.HelpElement.TitleText = "";
radPropertyGrid1.PropertyGridElement.SplitElement.HelpElement.ContentText = "";