Ajax Control Toolkit slider not rendering

Hi. I’m trying to add a slider control to a .aspx page using the Ajax Control Toolkit. If I add it to a clean page it renders correctly, but if I add the same code (see below) to a page with other content on it just renders as two text boxes without the slider extension kicking in. I’m not sure what in the other content is interfering with it, but for example, having a SQLDataSource on the page does.

Any suggestions as to where to go with this please?

<asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
</asp:ToolkitScriptManager>   
<asp:TextBox ID="Slider1" runat="server"></asp:TextBox>
<asp:SliderExtender ID="Slider1_SliderExtender" runat="server" Enabled="True" 
    Maximum="7" Minimum="1" Steps="7" TargetControlID="Slider1" BehaviorID="Slider1" BoundControlID="SliderValue">
</asp:SliderExtender>
<br />
<asp:TextBox ID="SliderValue" runat="server"></asp:TextBox>

Thanks
Jackie