"This type of SQL statement is not supported" when optimizing a valid SQL statement. (4234011)

When trying to optimize a statement, a "This type of SQL statement is not supported" error is given.

The query runs w/o problems. From Toad the query is sent to optimizer, and from there, use the green arrow icon to optimize, but it never optimizes and just gives the error.

Sample statement:
SELECT trv.CUST_633,
trv.EVNT_CD,
trv.POOL_ID
FROM evt_hist trv
WHERE inv.evnt_dt > (current date - 28 DAYS)
AND trv.evnt_dt != current date
AND trv.EVT_CD IN ('DD', 'AP')
AND (trv.cust_333, trv.cust_ST) = (trv.CITY_333, trv.cvn_ST)