SSO data issue - User 1 is able to see data of User 2

Hi,

We have configured SSO between SAP portal and R/3 such that , the users windows login credentials are used to login to SAP portal. It works fine for all users except for one. This user (user 1)is able to seem other user (user 2) data. For all other users it works absolutely fine. Any inputs on what might be the reason?

Regards,

Navya