You receive error messages when you try to edit the Web application monitoring settings in System Center Operations Manager 2007

Looks like microsoft posted the KB for this. KB 941977

SYMPTOMS

When you try to edit the Web application monitoring settings in Microsoft System Center Operations Manager 2007, you receive the following error messages:

Failed to load Web Application

Microsoft.EnterpriseManagement.Common.ObjectNotFoundException: Requested object(s) not found.

This problem occurs if a user in the Operator user role opens the Operations console when the user in the Administrator user role tries to edit the Web application monitoring settings.

http://support.microsoft.com/default.aspx/kb/941977