I am a new user. I need help.

When i export data from 9i db,get error message as follow:
exp-00008: ORACLE error 1422 encountered
ORA-01422: exact fetch return more than requested number of rows
ORA-06512: at "SYS.STANDARD", line 628
ORA-06512: at "SYS.DBMS)RULE_EXP_RULES", line 129
ORA-06512: at line 1
EXP-00083: The previous problem occurred when calling SYS.DBMS_RULE_EXP
Can anyone tell me how to fix this problem?
Thanks for all.

Best Regards.
Thomas Chang.