Very strange problem with form authentication

I have developed a website that has some private pages that require user login. The page is hosted on IIS 6 on a windows 2003 server and I am using the Helicon ISAPI rewrite tool to implement paths of the form /folder/page-name/ (ie, paths without the .aspx extension). When a user tries to access a protected page, he is taken to the /login/ page. On my local computer everything works fine. ON the server I have the following weird problem: When I go directly to the /login/ page to log into the website, after entering the correct username and password, I am taken to a page which does not exist and looks like /login/login.aspx If I type the address of a protected page, I am redirected to the /login/ page and after entering the login details, I am logged into the system. This is very weird and it looks like there is something weird with the ASP.Net setup on the server. I am using exactly the same procedure on another website which is hosted on a shared server and it works ok. The ...