Crystal Report Authentication Problem

Question

Hi All ,
I have a problem in my application.
I am using Asp.net 2.0 for my application.
I am creating crystal report using CrystalReportViewer.The Report is coming fine.But When I am trying to to export the report using ReportViewer Export Icon to MS Word ,  a dialog box is poping Up, asking for "Enter the network authentication". If We cancel also the report is not exporting.
Plz help me..........
Thanks & Regards
Trushna