I'm currently opening an aspx page (myModalASPX) as a dialog box from
client-side script using window.showModa lDialog(blah blah blah).

The dialog opens as expected. Now I'm adding functionality to the dialog
box/aspx page that causes a postback. What currently happens is that after
the postback, myModalASPX page is rendered back to the client in a new
browser window - which gives me *two instances* of myModalASPX...