Ajuda com erro JSF. Urgente

<h:selectOneMenu value="#{alunoController.aluno.cd_curso}">
	 <f:selectItems value="#{cursoController.listCombo}"/>
</h:selectOneMenu>
<h:commandButton action="#{alunoController.insere}" value="Cadastrar" />

public Map<String, Integer> getListCombo() throws SQLException
	{

		CursoDAO dao = new CursoDAO();

		TreeMap<String, Integer> map = new TreeMap<String, Integer>();
		for (Curso cd : dao.getList())
		{
			map.put(cd.getNome(),cd.getCd_curso());
		}
		return map;
	}