Your ontology is inconsistent which means that the OWL reasoner will
no longer be able to provide any useful information about the
ontology.  
You have several options at this point:
-  Click the Explain button to try the Protege explanation facility.
-  If you think you know what the problem is, click
  Cancel to fix the 
  ontology yourself.
-  Some reasoners come with command line tools that will provide
  complete explanations for inconsistent ontologies.