http://decipherinfosys.wordpress.com/2007/05/16/resolving-ora-24005-when-dropping-a-schema-or-a-table/
SQL> execute DBMS_AQADM.DROP_QUEUE_TABLE (queue_table => ‘DECIPHER_AQ_DEMO’, force => true);
Same can be used on getting ORA-24005 while dropping table