Got it...

here are some links that explains the problem

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q244465

http://groups.google.ca/group/comp.lang.python/browse_frm/thread/9748501bbfcdbca0/1560146f066d48aa?lnk=st&q=serialize+%22enable+session+state%22&rnum=1&hl=en#1560146f066d48aa



In brief, IIS serializes requests when sessions are enabled.


Disabling the session fix the problem.

Alex