I'm in the process of creating a module that will utilize the Ajaxtoolkit Modalextender.  My modal is setup as follows:

[code]<asp:LinkButton ID="linkbutton1" runat="server" Text="Some Text" Width="160px"></asp:LinkButton></td>

<ajaxToolkit:ModalPopupExtender ID="MPE1" runat="server" PopupControlID="pnlReplyPopUp" TargetControlID="linkbutton1" BackgroundCssClass="modalBackground" DropShadow="true" OkControlID="btnReply" CancelControlID="btnCancel" OnOkScript="Ok()">
</ajaxToolkit:ModalPopupExtender>[/code]

The only difference between my code above and the example code is around that the example uses a asp form control.  However, if you follow that approch, then you receive an error about multiple form controls.  So the issue is that when you click the link button nothing happens.  I assume that I can launch the modal window from the link button's Click event, however I'm not sure how you would call that since it's suppossed to be ajax code.

You don't need the <form> tags to make the LinkButton to work. However, you do need the scriptmanager to be loaded. The easiest way to do this is to check the box support partial rendering for each page in the Host->Module Definitions-><Edit of each individual Page>