I received an interesting error today while trying to ‘Manage Data Sources’ on a report “The resource object with classname ‘ReportServer’ and the key ‘DataSourceList’ was not found”:
I found that sometimes it would work, but other times it would fail. A bit of tracing showed that when I hit web1 in the farm it would fail, but web2 would succeed.
With this information in hand I hand a look at the App_GlobalResources folder under c:\inetpub\wwwroot\wss\virtualdirectories\<web application name>
Interestingly web2 (which worked) had some resources called ReportServer.resx, but web1 (which failed) did not have these resources, that was what was causing the failures.
I copied the resources across and the issue resolved itself.
I suspect that the report services add on wasn’t installed properly.