Issue:
If you are getting error when REST call is made to https://<<Org Name>>/xrmservices/2011/OrganizationData.svc/AccountSet(guid’FA18CED8-FBBB-E711-9110-005056B860DB’) saying Resource not found for the segment ‘AccountSet’. And if you trace this call in fiddler you might get response as HTTP/1.1 404 Not Found.
Resolution:
Reason for this error is User who is invoking this call does not have permissions to read the AccountId.
My Encounter with Dynamics CRM 