As I said earlier , we didn't test our solution to using the ModalPopupExtender in SharePoint in all situations. Today we made a start to do so. To indicate our successrate: we now use window.showModalDialog with some extra pages... Lets go through...
Getting the ModalPopupExtender from the Ajax Control Toolkit to work (decently) in SharePoint was not exactly a walk in the park. With a default SharePoint installation, the modal popup is partly positioned 'outside' of the page (you only see...