Problem with user authorization for the back end system

Dear all,

We have configured a back end SAP BW system with the Enterprise Portal for publishing BW generated reports. The users of the portal are mapped using a BW system user. But when we run these reports from the portal it still asks for a User ID and password for the BW system in a "pop up". The web browser is Internet Explorer. I'd be grateful if somebody can tell us how to solve this issue. Thanks a lot.

Regards,

Sumit