problem using oledb + informix

Hi all.
I have a problem writing a table on informix (IDS 10.0) using
a linked server on SqlServer Express:

This is the insert:

INSERT INTO unixdb1.practor.informix.ven_rilcld
(rilcld_rilcld,rilcld_entazi, rilcld_numter, rilcld_codbar, rilcld_qta,
rilcld_prezzo, rilcld_codart)
values( 11,'05019999', 0, '222', 45, 23, '')


And this is the error:

Msg 7343, Level 16, State 2, Line 5

The OLE DB provider "Ifxoledbc" for linked server "unixdb1" could not
INSERT INTO table "[unixdb1].[practor].[informix].[ven_rilcld]".


The same sql run without problem if I use a simple vbs script:
________________________________________________________________
Set cx = CreateObject("ADODB.Connection")
cx.provider = "Ifxoledbc"
cx.connectionstring = "Data
Source=practor@ol_server10_tcp;Server=ol_server10_tcp;Service=1531;Host=10.36.1.102;Protocol=olsoctcp;User
ID=informix;Password=$1nf0rm1x$;Persist Security Info=True;"
cx.Open

cx.Execute ("insert into ven_rilcld values
(0,'09876543',51,'73643234','',0,100)")
________________________________________________________________

Any suggestion?

T.I.A.

Stefano