When deleting a site, you get error: 500 INTERNAL SERVER ERROR. Error is just black text on white background, nothing else.
Some errors are logged into MOSS log:
There is no Web named "/SiteA/testi/_layouts/webdeleted.aspx".
Possible mismatch between the reported error with code = 0x81070504 and message: "There is no Web named "/SiteA/testi/_layouts/webdeleted.aspx"." and the returned error with code 0x80070002.
Simple.master page has been altered to brand the layout of different pages, which is causing the problem.
Revert Simple.master to original version that came with MOSS.
You cannot have
<wssuc:Welcome id="IdWelcome" runat="server" EnableViewState="false"></wssuc:Welcome>
on the simple.master page. Remove it and it works, if not, remove controls from the page one by one until you find out the one causing the error.