Hi Manjula,
Did you find any solution to this issue?
I am receiving the same error when I first open an application and a few seconds after I open again the same application with the same browser / PC.
I am using DS 1.3 SP02 over a BW 7.4
I haven't found any note / posts talking about this topic except for yours.
the most similar note I've found is 1044258 - BEx Web Applications Java: Server Session Timeout but it has nothing to do with DS alone.
Thanks in advance,
Juan Carlos