Matriz de objeto personalizado de .NET a VB6

I've written a small library in C#.

In this library there are two classes that are ComVisible.

The first one has a method that provide a array of custom objects (declared in the second class).

I tested the library with a small c# application and everything work. Then I do the same thing VB6. The problem occurs when I call the method I descibed before. I get a Type Mismatch error.

Here's the BV6 code:

   Private Sub Command1_Click()
       Dim Flussi As FMDriver.FMDriver  
       Set Flussi = New FMDriver.FMDriver
       [...]
       Dim temp() As FMDriver.FM
       temp = Flussi.GetElabData(station, codpar, data, tabella, nfunz, tiponfunz)
       [...]

This is the custom class FM

[ComVisible(true)]
public partial class FM
{
    public FM() { }

    [ComVisible(true)]
    public double Value { get; set; }

    [ComVisible(true)]
    public double IDisp { get; set; } 
}

Any idea? If from the response I extract only one element it works.

EDIT:

Another strange thing...

Dim pippo As FM
Set pippo = CreateObject("fmdriver.fm")
pippo.Value = 100
pippo.IDisp = 43    
pippo = Flussi.GetElabData( [..cut..] )(4)

In Pippo.Value there's the correct value that GetElabData return on the 4th position of the array but in Pippo.IDisp the value doesn't change, it remains 43instead of getting the new value.