Summary
On a sporadic basis you may encounter any one of the following errors while rendering reports in Reporter:
Index was outside the bounds of the array. Object reference not set to an instance of an object.
Index was outside the bounds of the array.
Object reference not set to an instance of an object.
Fix
The following Reporting Services hotfix resolves this issue:
http://support.microsoft.com/kb/959595
More Information
Install the hotifx on the machine where you run Reporter.
Sarah Henwood | Microsoft SQL Server Escalation Services