The text of the tabs inside a SlidingZone is not displayed properly when the SlidingZone is updated via AJAX. 

Steps to reproduce:
Run the following code and click a button inside a SlidingPane.

<telerik:RadSplitter ID="RadSplitter1" runat="server">
<telerik:RadPane ID="RadPane1" Scrolling="Both" Width="30px" runat="server">
<telerik:RadSlidingZone ID="RadSlidingZone1" runat="server" Width="30px">
<telerik:RadSlidingPane ID="RadSlidingPane1" runat="server" Title="Menu 1" Width="280px">
<telerik:RadButton runat="server" ID="btn1" AutoPostBack="true" Text="Update SlidingZone"></telerik:RadButton>
</telerik:RadSlidingPane>
<telerik:RadSlidingPane ID="RadSlidingPane2" runat="server" Title="Side Menu Two" Width="280px">
<telerik:RadButton runat="server" ID="btn2" AutoPostBack="true" Text="Update SlidingZone"></telerik:RadButton>
</telerik:RadSlidingPane>
</telerik:RadSlidingZone>
</telerik:RadPane>
<telerik:RadPane ID="AdditionalPane1" runat="server"></telerik:RadPane>
</telerik:RadSplitter>
<telerik:RadAjaxManager runat="server" ID="RadAjaxManager">
<AjaxSettings>
<telerik:AjaxSetting AjaxControlID="RadSlidingZone1">
<UpdatedControls>
<telerik:AjaxUpdatedControl ControlID="RadSplitter1" />
</UpdatedControls>
</telerik:AjaxSetting>
<telerik:AjaxSetting AjaxControlID="RadSlidingZone1">
<UpdatedControls>
<telerik:AjaxUpdatedControl ControlID="RadSplitter1" />
</UpdatedControls>
</telerik:AjaxSetting>
</AjaxSettings>
</telerik:RadAjaxManager>