This is because the dbExpress interface seems to insist on setting the schema name to the user name in the connection.ini file. For instance, in the following entry (where the user name is a Windows user account):
[sql_server] BlobSize=-1 Database=sql1 DriverName=ODBC Password=pwd User_Name=Nick Gorham
the dbExpress interface will set the schema of the SQLTables call to "Nick Gorham".
This may be what you want, but in most cases it won't be. The solution is to use the alternative connection method by encoding the user name in the connect string and leaving the User_Name field empty. The tables call is then made with no specified schema:
[sql_server] BlobSize=-1 Database=DSN=sql1;UID=Nick Gorham;PWD=pwd DriverName=ODBC Password= User_Name=