Oracle Database Discussions

Hello all.
i am trying to convert an sql server 2005 into oracle 10g using sqldeveloper 1.5.
a table in sqlserver having nvacharmax column - supposed to be migrated into clob (according to the data map).
how ever when i look at the script for creating the oracle objects, I see those columns written as nvarchar2(0) - which obviously can not be .
if I run the conversion using nvachar2(size) - some data "fails" because the it is to long for varchar2 column .
if i set the table to be created with clob - all data being migrated but i see "bad" data .like(question marks etc') .
so . is it a bug in sqldeveloper ? am i doing something wrong ?

thanks

S.

p.s.
I have posted this question in SQLDEVELOPER forum as well, but I guess this is more suitable forum .
so apologies for those who saw this thread at the other forum as well.