Hello Shaneel,
From the error message, it looks like there is some proxy involved, is there a proxy involved between your SAP and the sharepoint ?
You can check your internet explorer or any other browser you used for the proxy server details.
Try and configure proxy server details as explained in : http://help.sap.com/saphelp_nwpi711/helpdata/en/48/479b6163524bb9e10000000a42189b/frameset.htm
You need to specify your windows logon credential as userid and password.
Regards,
Siddhesh