I have spent a day and a half trying to resolve this issue. Bascially have an ASP.net website with Forms Authentication on IIS7 using Framework 4.0.
The Authorizati
I was seeing this same problem when attempting to hit the root path and I tried everything previously mentioned. It seems Asp.net 4.0 adds two ExtensionlessUrl modules to applicationhost.config for IIS 7. You can remove these modules by adding the following to your web.config
Additional Information
Microsoft KB
How extensionless urls are handled by asp net v4