Error while running a SSRS 2005 report in Internet Explorer-Collection of common programming errors

We have developed a report using SSRS 2005. This is embedded in the web application, which is built on C#/ASP.Net (3.5 framework/VS 2008).

The report is deployed in a report/db server, which is a part of two tier architecture ie. app and db. This report takes more than an hour for execution and producing the output, as it calls a stored procedure which processes large amount of data. When the report is being run, and elapsed time is close to an hour, then an error message is displayed as: “Internet Explorer can not display the webpage”.

Event viewer log has following message:

Event Type: Warning
Event Source:   ASP.NET 2.0.50727.0
Event Category: Web Event 
Event ID:   1309
Date:       1/7/2013
Time:       10:58:04 AM
User:       N/A
Computer:   --------------------
Description:
Event code: 3005 
Event message: An unhandled exception has occurred. 
Process ID: 7456 
Process name: w3wp.exe
Account name: NT AUTHORITY\NETWORK SERVICE
Exception type: AspNetSessionExpiredException 
Exception message: ASP.NET session has expired 
Request URL:http://------/ABC/Reserved.ReportViewerWebControl.axd?ReportSession=1ki0jo3ouutixi555breaja4&ControlID=9ab46efcbab44cb987c5b9967fea54c3&Culture=1033&UICulture=1033&ReportStack=1&OpType=SessionKeepAlive&TimerMethod=KeepAliveMethodctl00_ContentPlaceHolder1_ReportViewer1TouchSession0