400 Session timed out - please log in again

Hi Expert,

What could be the reason for the following error message:-

400 Session timed out - Please login again

Error: -11

Version: 7000

Component: ICM

Date/Time: Sat May 23 10:53:03 2009

Module: icxxthr_mt.c

Line: 1705

Server: sapapp28_PRD_28

Error Tag: {-}

Detail: Session does not exist

This error is coming while running on ITS in Portal.

This problem has started after we have upgraded to ECC6 version.

When user executes a workitem in portal inbox a timeout error message pops up while clicking on End Execution button.