vb client using a delphi com object

i ve looking for a while , if anyone has a clue ....

i m trying to use an activex i wrote in delphi.
i can use this object fine in a delphi client but not in a vb client.

i supect that there is a pb with the widestring type and vb,
for i can use (still in a vb client) an activex fonction with an integer for
output.

here is the code of the vb client (which crashes)
Dim obj As dll_string_2.cls_string2
Set obj = New dll_string_2.cls_string2
MsgBox obj.rndfile("toto")

here is the same working code for a delphi client
procedure TForm1.Button1Click(Sender: TObject);
var obj:Icls_string2 ;
ws:widestring;
s:string;
begin
s:='toto';
ws:=s;
obj:=Cocls_string2.Create ;
showmessage(obj.rndfile(ws));
end;

and finally here is the code for the delphi activex object
function Tcls_string2.rndfile(out val1: WideString): WideString;
var
      s : string;
      ws : WideString;
begin
s:='test';
ws:=s;
   result:=ws;
end;

thx a lot
erwan