Hello,
I am trying to reproduce the problem using your code (and several variations of it), unfortunately without much success. It works great for me (see screenshot attached). and I am really lost as to what might be going on. Here is my setup:
<cc1:WebDialogWindow ID="WebDialogWindow1" runat="server" Height="300px" Width="400px">
<ContentPane>
<Template>
Test
</Template>
</ContentPane>
</cc1:WebDialogWindow>
<cc1:webdialogwindow id="WebDialogWindow2" runat="server" width="310px" height="185px"
left="0" top="10px" style="z-index: 30; line-height: normal;">
<ContentPane>
<Template>
<asp:Label ID="lblTest" Text="AAA" runat="server"/>
</Template>
</ContentPane>
</cc1:webdialogwindow>
<input type="button" onclick="$find('<%=WebDialogWindow1.ClientID%>').set_windowState($IG.DialogWindowState.Normal);"
value="OPEN" />
Is it possible that you have global CSS settings for some of your HTML elements (e.g. global <div> , <table>, etc settings) that may interfere with the dialog window in some way?