Hi Balaji,
Since the time out is not happening when you set the user parameter, "WCF_IGNORE_ENHANCEMENT" as 'A', it seems like the issue is something related to do with the custom enhancements made to Service Contract Header page. Review the custom enhancements made to the Service Contract Header page first. Set a breakpoint in the associated inbound plug method of the window controller and see if any exception is being thrown causing the system to time-out. Else set a breakpoint in the do_prepare_output method of the header view and see what is going on.
Hope this helps.
Regards,
Prathap