Problem with Forms Authentication and Reporting Services

I have a working production environment of SQL Server Reporting Services开发者_高级运维 2008 that is configured for Forms Authentication. I have been trying to setup a new environment that uses the same custom authorization extension dll. Unfortunately, it is not working. The original creators of the dll and environment configuration are not available.

I have verified that the LogonUser method in the extension DLL return true for valid credential and false for invalid credentials. So I know that the DLL is working and configured to access the database correctly.

The logon page is getting a successful return from the LogonUser web service method in Reporting Services, Fiddler shows that it has the authCookie, and it is being redirected to http://myurl/ReportManager/Pages/Folder.aspx as I beleive it should. But when redirected to this page Fiddler shows me that the authCookie is not being sentback out by the browser. Without the auth cookie, Reporting Services goes right back to the custom login page. The same workstation and same browser does not exhibit this behavior when it accesses the working legacy instance.

I struggled over whether this should be here or on Server Fault. I originally chose Server Fault because the extension dll is working in another environment and all of my testing shows that the problem is not in the dll. That lead me to the conslusion that the issue is a Reporting Services configuration issue. However, the complete lack of response on SF (and very few views), and the complete lack of knowledge about forms authentication by my IT department has caused me to reconsider and post the question here on SO.

Thanks in advance,

Jim

Edit

I installed Firefox and a couple of add-ins, then reran my tests. The observed behavior on the surface is identical to IE. However, Fiddler shows that Firefox is sending the auth cookie when it redirects to /ReportManager/Pages/Folder.aspx(as mentioned earlier IE does not do this). But Reporting Services appears to be ignoring it and still redirects to the login page. The cookie editor addin says that the cookie has the name 'authCookie' and the site is "my domain.com".

To me this seems to all be correct except for the fact that RS keeps redirecting to the login page. Why?