Semantic annotations describe the semantics of artifacts like documents, web-pages, schemas, or web-services with concepts of a reference ontology. Application interoperability, semantic query processing, semantic web services, etc. rely on a such a description of the semantics. Semantic annotations need to be created and maintained. We present a technique to detect logical errors in semantic annotations and provide information for their repair. In semantically rich ontology formalisms such as OWL-DL the identification of the cause of logical errors can be a complex task. We analyze how the underlying annotation method influences the types of invalidations and propose efficient algorithms to detect, localize and explain different types of logical invalidations in annotations.