it's the first time that I write :-D

I have a problem with MS SqlServer2K and Oracle.
I create a linked server on SqlServer and I need to insert rows in a table of Oracle.
The SQL is :
insert into [MYoracle]..[MYnamespace].[MYtable] (field1,field2,field4) values (value1, value2,value3).

The field3 of the oracle table is set to: "allow null" but it is ignored during the insert! With Ms SqlServer7.0 averything works, the problems comes with Ms SqlServer2k, it goes in error :

OLE DB provider 'MSDAORA' could not INSERT INTO table '[MYoracle]..[MYnamespace].[MYtable]' because of column 'field3'. The column used the default value.
[OLE/DB provider returned message: Multiple-step operation generated errors. Check each status value.]
OLE DB error trace [OLE/DB Provider 'MSDAORA' IRowsetChange::InsertRow returned 0x80040e21: Data status sent to the provider: [COLUMN_NAME=field1=DBSTATUS_S_OK], [COLUMN_NAME=field2 STATUS=DBSTATUS_S_OK], [COLUMN_NAME=field4 STATUS=DBSTATUS_S_OK]

I found an old message about this in <a src='http://dbforums.com/arch/210/2002/9/507770'>archive</a> but without answers :'(

can onyone help me please