Change your case, as it looks like your database layer is automatically quoting it if you use CamelCase.
A quick test in a Firebird 2.5 database here shows:
SQL> select t1.usuario, t1.NoExisto from sg_usuario t1;
Statement failed, SQLSTATE = 42S22
Dynamic SQL Error
-SQL error code = -206
-Column unknown
-T1.NOEXISTO
-At line 1, column 23
SQL> select t1.usuario, "t1.NoExisto" from sg_usuario t1;
Statement failed, SQLSTATE = 42S22
Dynamic SQL Error
-SQL error code = -206
-Column unknown
-t1.NoExisto
-At line 1, column 34
As you see, the database engine generates an error with camel case only when it gets the SQL query using quotes.
I suggest you to try myfield_id or use the correct case you have in your field name.
select
table1.pkfield1,
table1.field_no,
table1.fk1_id,
table1.fk2_id,
table1.myfield_id,
table1.bfield,
table2.desc1,
table2.desc2,
table2.desc3
from table2
right outer table1 on (table2.pk1_id = table1.fk1_id)
Order by table1.fk1_id, table1.field_no desc