Report Viewer Webpart Error

While establishing a Report Viewer webpart connection with Report Explorer webpart, I was getting following error:

System.Security.SecurityException: Request for the permission of type 'Microsoft.SharePoint.Security.SharePointPermission, Microsoft.SharePoint.Security, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' failed.


After digging into this error I figured out that sharepoint site is running under application pool using "Network Service" account.

In order to resolve aforementioned issue, I did the following things

1- Go to Central Admin --> Operations
2- Click "Service Accounts" under (Security Configuration) and do the following

After specifying domain account credentials it solved the issue.

Hoping this will save someone time in future.