Cookies issue in EP portal

Dear Experts,

We are using Enterprise portal(Component Version : SAP EHP 1 for SAP NetWeaver 7.0) for Stock confirmation, Order confirmation and R/3 report access in customer level.

Last week we have upgraded EHP6 (Component Version : EHP6 FOR SAP ERP 6.0). Post up gradation we are facing few issues in Customer Portal(EP).

One of our high priority issues as below:

In EP our portal, Customer can access some reports by calling R/3 transaction via iView. The actual problem was the customer A having two ID's and logon in a EP system using his first ID to viewing the reports and logged off. Using second ID he logged into same EP system and accessing the same report, the time when he open the report iView displaying the same input screen of first ID(System details also showing first ID's ). It is happening in Internet explorer version 9. No changes even if we deleted the cookies.

But its working fine in Mozilla firefox if we deleted the cookies before starting second ID.

Waiting for your solution.

Vasanth S