[FIXED] Buttons in window doesn't work?

[Dan]

I tried to put buttons in my window like follow:

<cool:Window ID="Window1" runat="server" AutoShow="true" Collapsible="true">
            <Buttons>
                <cool:Button ID="Button1" runat="server" Text="Submit">
                </cool:Button>
            </Buttons>
</cool:Window>

and it gives me errors

[InvalidOperationException: Cannot Modify Control Collection]   Coolite.Web.UI.SingleChildControlCollection.Add(Control child) +46   Coolite.Web.UI.PanelBase.CreateChildControls() +85   System.Web.UI.Control.EnsureChildControls() +87   System.Web.UI.Control.PreRenderRecursiveInternal() +50   System.Web.UI.Control.PreRenderRecursiveInternal() +170   System.Web.UI.Control.PreRenderRecursiveInternal() +170   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2041

As an alternative, I put the buttons in my content but I have to play with the html to position it the way it does it in ext. Am I doing something wrong?

Thanks