Microsoft Access Not finding correct Linked SqlServer records

Microsoft Access 2010 application is not returning the correct linked records from a SqlServer 2008 database.

For simplicity on the Access side I have a query such as:

column XYZ is defined on the SqlServer as Nvarchar(1);

Select * from LinkedSqlTable where XYZ in ("D","F","X");    

However, it is returning records where XYZ = capital I or capital A only.

If I run a similar query via Management Studio on SqlServer

Select * from LinkedSqlTable where XYZ in ('D','F','X');   

 then the correct D, F or X records are returned.

I have tried using ... Trim(XYZ) in  ("D","F","X");  

                            ...  trim(XYZ) = "D" or trim(XYZ) = "F" or trim(XYZ) = "X";

and in a separate query I have grouped the records to verify the values I am looking for exist and do not have spaces or some special character attached in some way.

I would appreciate any ideas.