Hi Sandip,
Please take http traces using a sniffer such as httpwatch/fiddler. please make sure that
the portal and the backend calls are using the same protocol (http/https) and the same domain
(e.g portal.domain.com is calling backend.domain.com).
you can see more information in SAP notes 654982,
632440 and 1334956. Also refer to the SAP help:
http://help.sap.com/saphelp_erp2005/helpdata/en/67/be9442572e1231e10000000a1550b0/content.htm
Best regards,
Etay