SQL & PL/SQL :: ORA-00904 Reading Via Dg4SQL Gateway From SQL Server 2008

I have trouble reading a field called "Description" from a SQL Server 2008 DB using the gateway:

SQL> select "Description"
from opportunity@mscrm
select "Description"
from opportunity@mscrm
*
Error at line 1
ORA-00904: "Description": ungültiger Bezeichner

My first thought was, that "Description" was a reserved word in Oracle but it's not:

SQL> create table delete_this ("Description" varchar2 (50 char))
Table created.
SQL> select "Description" from delete_this
no rows selected.

So everythings fine here. Then I thought, that I might have mispelled the column name, but no:

SQL> select column_name
from v_mscrm_tab_columns
where table_name = 'opportunity'
and column_name like 'Desc%'

[code]....