Microsoft Report Server - ReportViewer Timeout Problem

Question

Hi, We are using Microsoft Report Server 2005 and getting reports from asp.net page by using ReportViewer. We have a situation about timeout;

There no timeout error when using report server in local mode

We get timeout error when using report viewer in an asp.net page and the pages are less than 40

We get timeout error when using report viewer in an asp.net page and the pages are more than 40

What should we do? Thanks