SQL "IN" clause in BDE 2.52

I am hoping someone can help me with this one.

I have a D1 application with a TQuery where the SQL is as follows:

select agent_code, course_code, "M" as req_type, "10/22/97" as
expiration
from mandetl
where Course_Code in ("BULL","NHQC")
and Office in ("Baltimore","Salisbury POD")

When I execute this, DBD version 5, I get the message "query appears to
ask to unrelated questions".  The same syntax run in DBD version 7 runs
correctly.

1.    Is there a practical limit on the number of "IN" clauses you can
have in a BDE 2.52 SQL statement?
2.    If there is no limit, how do I phrase the SQL properly so that it
will execute.