Cannot complete a review due to Foreign Key Constraints

I have a review that when they try to complete it throws an error exception:

2015-01-02 11:31:36,019 WARN [qtp454631513-3417171 ] org.hibernate.util.JDBCExceptionReporter JDBCExceptionReporter-logExceptions - SQL Error: 1451, SQLState: 23000
2015-01-02 11:31:36,020 ERROR [qtp454631513-3417171 ] org.hibernate.util.JDBCExceptionReporter JDBCExceptionReporter-logExceptions - Cannot delete or update a parent row: a foreign key constraint fails (`fisheyedb/cru_comment`, CONSTRAINT `FKE5A1D10674DF349C` FOREIGN KEY (`cru_reply_to_comment_id`) REFERENCES `cru_comment` (`cru_comment_id`))
2015-01-02 11:31:36,021 ERROR [qtp454631513-3417171 ] org.hibernate.event.def.AbstractFlushingEventListener AbstractFlushingEventListener-performExecutions - Could not synchronize database state with session
org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)

I am not sure what to do with this.

Please help