Invalid LOV query error

Question

I am trying to modify a query for LOV page item but get an Invalid LOV query error when trying to Apply Changes to my page(query however works in SQL*Plus)
I am trying to change the date format of query result to MON YYYY.
Original query that works:
select distinct bill.BILLED_DATE display_value, bill.BILL_ID return_value
from BILL;
New Query that fails in APEX (but works in SQL*Plus)
select distinct to_char(bill.BILLED_DATE, 'MON YYYY') display_value,
bill.BILL_ID return_value from BILL;
Anyone have any idea what I need to do to make this work?
"1 error has occurred
LOV query is invalid, a display and a return value are needed, the column names need to be different. If your query contains an in-line query, the first FROM clause in the SQL statement must not belong to the in-line query"

Answer 1

Strange, this lov does work and is no different than yours:
select distinct to_char(sysdate,'MON YYYY') disp, 1 retval from dual
What are the results from the query? Can there be something wrong with that?
Regards Guido