I am having a problem with attempting to hide panes and show panes within the splitter control. I have a demo that I can upload if needed.
When you attempt to hide a pane and splitter it throws js error.
The code below will thow the error (from your examples). If you make the RadPane2 back to visible the JS error will quit happening. The splitter control is looking for that object. As a work around I leave that pane RadPane2 visible but turn off the splitbar and slidingzone as shown. Ideally we should be able to turn the visibility off
<
telerik:RadSplitter id="RadSplitter1" runat="server" width="700" height="500">
<telerik:RadPane id="RadPane1" runat="server" width="22" scrolling="none">
<telerik:RadSlidingZone id="RadSlidingZone1" runat="server" width="22">
<telerik:RadSlidingPane id="RadSlidingPane2" title="Pane1" runat="server" width="150">
Pane 1 Content
</telerik:RadSlidingPane>
</telerik:RadSlidingZone>
</telerik:RadPane>
<telerik:RadSplitBar id="Radsplitbar1" runat="server" ></telerik:RadSplitBar>
<telerik:RadPane id="MiddlePane1" runat="server" Scrolling="None">
<telerik:RadSplitter id="Radsplitter2" runat="server" height="400"
width="700" Orientation="Horizontal" Visible="True">
<telerik:RadPane id="Radpane2" Visible=False runat="server" height="22" scrolling="none">
<telerik:RadSlidingZone id="Radslidingzone2" Visible="False" runat="server" height="22" SlideDirection="Bottom">
<telerik:RadSlidingPane id="Radslidingpane5" title="Pane1" runat="server" height="150">
Pane1</telerik:RadSlidingPane>
</telerik:RadSlidingZone>
</telerik:RadPane>
<telerik:RadSplitBar id="Radsplitbar3" Visible=False runat="server"></telerik:RadSplitBar>
<telerik:RadPane id="Radpane4" runat="server">
<div style ="padding:5px">
<h2>New product updates and features coming soon </h2>
</div>
</telerik:RadPane>
</telerik:RadSplitter>
</telerik:RadPane>
</telerik:RadSplitter>