Records with Null Fields Don't Refresh

I have inherited a bunch of Excel spreadsheets that pull in data from Access databases using "Connections." I am eliminating them one by one, as I do not like this method for a number of reasons. But I have encountered something weird.

When the source of the connection has a null value in one of the refresh field, the record doesn't come into Excel. If I copy the source query out of the "Connection/Properties" box, clean out the apostrophes and put brackets around table or field reference with spaces in it and then run the query, the records with nulls show up. But when I run the refresh inside Excel, they don't.

Has anyone encountered this before. I have now found it in three different situations, and if this is a flaw in the Connection/Refresh method I've got a bunch of people who may be getting faulty data - at least until I can change the way their workbooks get populated.

Thanks.