I venture to say this is your problem http://allenbrowne.com/bug-18.html
While your conditions are not exactly as described, you are including a memo field in a query where 2 fields are not indexed.
I indexed the two joined fields and the problem went away, although I had to put notes in all the fields to get any notes returned in the result.
Is this a real example of how you have named and joined fields in your tables? If so, you probably often make your task much harder than it needs to be when it comes to getting reliable data in or out. I would elaborate, but maybe you are already quite proficient in normalization and simply threw this together.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.