SSO not working

Hi All,

I have configured SSO between R/3 ans EP system.They both are in the same domain.I did all the necessary steps for the configuration.

After doing the RFC transaction in R/3 and tested I wanted to login to the portal with the Admin id,but it is not allowing me to go beyond the login page.When I provide an invalid userid it is prompting user authentication failed.Wat might the reason for this.It is not showing any error at all.

Helpful answers will be rewared.

Regards,

Balaji S