#error results in unmatched records of outer join

Doing a simple query where I join a master table with all records and a query
that creates a subset of data. When I look at the result set after the join,
the master table records that aren't present in the subset have #error for
that column. My environment is Access 2002 on Xp Pro with all os and office
updates current. I've been doing this for some time and this is the first
time I've seen this. Thanks in advance for you help.
Steve