Problem in COM Callable Wrapper

i am creating a CCW and use it in VB 6.0 application. I have created two classes, ClassA and ClassB in .NET wrapper.
I am able to get the methods and properties of these classes in VB 6.0. My problem is that I am trying to create an array of object of classA in vb 6.0 and trying to pass this array in one of the method of ClassB. But I am getting runtime error.

Error Message displayed is:
----------------------------
Run-time Error '5':
Invalid procedure call or argument

----------------------------

Here is the VB code,

    Dim objB As New wrapperCls.ClassB
   
    Dim objA As New wrapperCls.ClassA
    Dim arrObjA(1) As New wrapperCls.ClassA
   
  
    objA.CurveName = "Curve1"
    objA.Date = "12122007"
    objA.DeliveryPeriod = "2"
    objA.DeltaPosition = 32.232
    objA.GammaPosition = 4.34
    objA.Peakness = "3"
    objA.RiskType = "Low"
    objA.TimePeriod = 2
    objA.uOM = "MMBTU"
    objA.uOM = "UMB"
   

    Set arrObjA(0) = objA
   
    objB.CorrectionNeeded = True
    objB.Counter = 2
    objB.DiscountNeeded = True
    objB.Method = "SampleMEthod"
    objB.NodeId = 3
    objB.UserId = "Bhupi"
    objB.VolNeeded = True

    objB.getPositionDataVO adPDataArr   ''' error occurs at this line

.NET CODE
===========
/** Interface declaration **/

 [Guid("CDD5E142-1CC1-4a76-A9E6-A415E2C41FD0")]
 [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
 public interface _ClassB
 {
  [DispId(21)]
  bool CorrectionNeeded{get;set;}
  [DispId(22)]
  int Counter{get;set;}
  [DispId(23)]
  bool DiscountNeeded{get;set;}
  [DispId(24)]
  string Method{get;set;}
  [DispId(25)]
  int NodeId{get;set;}
  [DispId(27)]
  string UserId{get;set;}
  [DispId(28)]
  bool VolNeeded{get;set;}
  [DispId(29)]
  void getPositionDataVO(ref AdhocPositionDataVO_Wr[] arrPDV);
 }

/** Class B **/

 [Guid("1FA539FE-DE70-4e4e-B598-74BA2DA41447")]
 [ClassInterface(ClassInterfaceType.None)]
 [ProgId("AdHocVar.AdhocInputMessageVO")]
 public class AdhocInputMessageVO_Wr: _AdhocInputMessageVO_Wr
 {
  public AdhocInputMessageVO_Wr() {}

  private bool _CorrectionNeeded;
  private  int _Counter;
  private bool _DiscountNeeded;
  private string _Method;
  private int _NodeId;
  private AdhocPositionDataVO_Wr[] _PositionDataArray;
  private string _UserId;
  private bool _VolNeeded;
  private AdhocPositionDataVO_Wr _PosData;

  public bool CorrectionNeeded
  {
   get{return this._CorrectionNeeded;}
   set{this._CorrectionNeeded =value;}
  }
  public int Counter
  {
   get{return this._Counter;}
   set{this._Counter=value;}
  }

  public bool DiscountNeeded
  {
   get{return this._DiscountNeeded;}
   set{this._DiscountNeeded=value;}
  }
  public string Method
  {
   get{return this._Method;}
   set{this._Method=value;}
  }

  public int NodeId
  {
   get{return this._NodeId;}
   set{this._NodeId=value;}
  }

  public string UserId
  {
   get{return this._UserId;}
   set{this._UserId=value;}
  }
  public bool VolNeeded
  {
   get{return this._VolNeeded;}
   set{this._VolNeeded=value;}
  }

  public void getPositionDataVO(ref AdhocPositionDataVO_Wr[] arrPDV)
  {
   this._PositionDataArray = arrPDV;
  }

 }

any reply will be highly appreciated.....

Thanks,