Statement below is working on Oracle 9i but not on Oracle 11g

SELECT *
FROM
(
    SELECT 0 scrnfail_rate, '9' zz, 7 hh FROM DUAL
    UNION ALL
    SELECT 0 scrnfail_rate, '9' zz, 7 hh FROM DUAL
)
WHERE zz IS NOT NULL
AND TO_CHAR (hh) NOT IN
(
    SELECT
        DECODE
        (
            scrnfail_rate, 0, -1,
                ROUND (LEVEL * 1 / (scrnfail_rate / 100)) 
                - 
                ROUND (1 / (2 * (scrnfail_rate / 100)))
        ) AS nno
    FROM   DUAL
    WHERE   NVL (scrnfail_rate, 0) > 0
    CONNECT BY   LEVEL <= ROUND(9 * scrnfail_rate / 100)
)

It looks like Oracle 11g is ignoring where decode or even where clause in the subquery. This query should return two rows as it does on Oracle 9i, but results ORA-01476: divisor is equal to zero on Oracle 11g EE 11.2.0.1.0 - 64bit.

Can anyone help? Thanks!