Problem with SSO between EP and ECC

Hi Experts,

  I have implemented the SSO between ep 7.4 and Ecc 6.0 with SSO configuration between SAP Portal 7.3 and ECC 6.0 Ehp 6.

But,when i try to test SSO with the tcode its asking for the username&password,

When i logoff and login its not asking the username and password(first time its asking the Uname&pwd).

When i close the browser and open the browser once again, the SSO fails.

Can any one tell me how to trouble shoot the issue??

Regards,

Anil