Login screen after stays after succsessful login

[dsuvankar]

Hi,
I am new to roundcube. Platform is Windows 2000,IIS. My php is running as CGI/FastCGI. After giving correct username and password it stays in the login page. The URL containing /?_task=mail

If I gave wrong username & password it throws invalid error in index page.

Any suggestions are welcome.

[SKaero]

Is there anything in your error log?