IWAUTH cookie not getting set using ActiveResponse module

Vips

Hi, I have configured TS 671 SP1 against the SiteMInder based on the ActiveResponse module. I have also configured LDAP against TS and the Policy Server.
The problem I am facing is that the user is asked for the Login credentials twice, once for the authetication from SiteMInder end and then again from the TS end. It appears that the IWAUTH doesnt get set properly when I login the first time and hence I am asked for the login again.

Can some one provide the pointers towards the problem that why IWAUTH is not getting set at the first login.

Also can some one provide the answer to follwoing questions.

1. When I am using the ActiveResponse do I need to update the following files with SSO specific entries. --
iw.cfg --> SHould I have "authenticate_by=sso" entry in iw.cfg.
2. application_custom.xml -- Do i need to update the application_custom.xml with default-param specific to SSO in ActiveResponse based paradigm?

Thanks in advance.