HttpHandlers / Modules :: HttpModule Broken After Migration To IIS7 (integrated Mode)?

In IIS6 the scenario below is working perfectly.I have an HttpModule called URLRedirect which examines URLS and by using RegEx rewrites of applicable. An example is a URL "/doc47.pdf" gets redirected to docpdf.ashx?id=47 Then the docpdf.ashx used the id value and, using a database builds an application/pdf document and returns it. Since I need to validate that the user has access to the data, the first line of the ProcessRequest(HttpContext context) function is:if (context.User.Identity.IsAuthenticated) ..... This is where the problem occurs, but more details first.

On a webpage, access to which is restricted to lgged on users who meet certain criteria there is a link which allows the user to present the page as a PDF document. This is achieved by using javascript to open a popup window using the window.open("/doc47.pdf", ... ) function.This all works fine under IIS6 and under IIS7 if I change the mode to Classic. But, under IIS7 in integrated mode, the following happens.The line in doc.ashx described above raises an exception because context.User == null. But, and this is interesting, if instead of using the link that opens the popup window I instead type /doc.pdf?id=47 into the address bar, the PDF document displays correctly.So this indicates to me that the URLRedirect Module is somehow losing the logged on user information.