Hi Apu,
I also got same error when I worked on SF integration.
Check below notes:
1838921 is the exact one...
1838921 - Multiple cookies in HTTP Headerand 2068581 - Multiple cookies and proxy authorization for Axis CommonsHTTPSender handler.
Could you please check whether we already implemented the Notes or not?
For your reference please check the Note 2150199 - "Invalid SFAPI Session" error message in SAP PI Interface for BizX to SAP HCM Integration