Database Software

RDBMS Version: 8.1.7.3
Operating System and Version: Windows 2000
Error Number (if applicable): EXP-00008
Product (i.e. SQL*Loader, Import, etc.): Export

EXP-00008: ORACLE error 1403 encountered

I try to export 1 database user and get an error:
. exporting posttables actions
EXP-00008: ORACLE error 1403 encountered
ORA-01403: no data found
ORA-06512: at "SYS.DBMS_AQ_IMPORT_INTERNAL", line 77
ORA-06512: at line 1
ORA-06512: at "SYS.DBMS_SYS_SQL", line 1118
ORA-06512: at "SYS.DBMS_SQL", line 316
ORA-06512: at "SYS.DBMS_EXPORT_EXTENSION", line 84
ORA-06512: at "SYS.DBMS_EXPORT_EXTENSION", line 135
ORA-06512: at line 1
EXP-00000: Export terminated unsuccessfully

I've done some search on metallink for "EXP-00008: ORACLE error 1403
encount" and already found piece of advice to delete some
system objects
DELETE FROM SYS.EXPACT$ WHERE FUNC_PACKAGE = 'DBMS_AQ_IMPORT_INTERNAL'

BUT I think it is not for me, because this database user has
several queue tables:
SELECT * FROM dba_queue_tables
Extract from query output:
CONTROL_QUEUE_TABLE OBJECT RIA.CONTROL_QUEUE_MESSAGE_T
FEEDBACK_QUEUE_TABLE OBJECT RIA.FEEDBACK_QUEUE_MESSAGE_T
INPUT_QUEUE_TABLE OBJECT RIA.INPUT_QUEUE_MESSAGE_T
JOB_QUEUE_TABLE OBJECT RIA.JOB_QUEUE_MESSAGE_T
OUTPUT_QUEUE_TABLE OBJECT RIA.OUTPUT_QUEUE_MESSAGE_T

What could be the reason for the error and what could be
the workaround ?

Thanks in advance,
Viacheslav