I recently had the issue described in this article http://www.njevity.com/blog/cannot-create-new-entity-dynamics-crm-after-migrating-dynamics-crm-online-dynamics-crm-premise after a migration from Dynamics CRM Online to OnPremise.
The following error was logged in the trace file, System.Data.SqlClient.SqlException (0x80131904): The EXECUTE permission was denied on the object ‘sp_MS_marksystemobject’, database ‘mssqlsystemresource’, schema ‘sys’.
The resolution was (as per the article) to grant execute access to the stored procedure:
grant execute on object::sp_MS_marksystemobject to [DomainSQLAccess Group {GUID for group}]where Domain is the name of the AD domain in which the SQLAccess Group is contained and GUID is the id that is part of the SQL Access Group name.