ASP.NET 2.0 Tip: 'Theme' is not a member of 'ASP.default_aspx'

Ever had an error like 'Theme' is not a member of 'ASP.default_aspx' on ASP.NET 2.0, like I had just now? The point was that there was no problem at all with the Theme, it always worked as it should. What indeed was the point was a long time ago I changed the default.aspx page name into something more useful. But.. the Page directive keeps saying

    1 <%@ Page Language="VB" AutoEventWireup="false" Inherits="_Default" %>

for reasons still unbeknown to me it turned out quickly this was fine on my (WinXP/IIS5) local machine, but not on the test server (Win2003/IIS6) on which I published the project. It came up with the above error.

Hope this helps you out someday.