Just an FYI that we posted a solution to the error above over on our new OperationsMgr blog:

http://blogs.technet.com/operationsmgr/archive/2009/01/27/opsmgr-2007-error-running-report-message-loading-reporting-hierarchy-failed-access-is-denied.aspx

Enjoy!

J.C. Hornbeck | Manageability Knowledge Engineer