What is wrong with this query?

As part of an error trapping routine, I'm having a problem with what should be a fairly simple query.

First, the query:

select bill_acct_id from transmission
where bill_acct_id not in (select acct_id from convert_acct);

Basically, I want a list of all 'bill_acct_id's in the 'transmission' table that are not in the conversion table (convert_acct). I know for a fact that there are bill_acct_id's not in the conversion table, yet the query returns no rows. Why?

TIA,
Joe

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Joe Nardone   |  Sundown dazzling day, gold through my eyes, but my eyes
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