Exception thrown while marshaling breaks the browse. It should be handled, like that:
/// <summary>
/// Unmarshals and deallocates a OPCITEMPROPERTY structures.
/// </summary>
internal static ItemProperty GetItemProperty(IntPtr pInput, bool deallocate)
{
ItemProperty output = null;

  if (pInput != IntPtr.Zero)
  {

    output = new ItemProperty();
    try
    {
      OpcRcw.Da.OPCITEMPROPERTY property = (OpcRcw.Da.OPCITEMPROPERTY)Marshal.PtrToStructure(pInput, typeof(OpcRcw.Da.OPCITEMPROPERTY));

      output.ID = GetPropertyID(property.dwPropertyID);
      output.Description = property.szDescription;
      output.DataType = OpcCom.Interop.GetType((VarEnum)property.vtDataType);
      output.ItemPath = null;
      output.ItemName = property.szItemID;
      output.Value = UnmarshalPropertyValue(output.ID, property.vValue);
      output.ResultID = OpcCom.Interop.GetResultID(property.hrErrorID);

      // convert COM DA code to unified DA code.
      if (property.hrErrorID == ResultIDs.E_BADRIGHTS) output.ResultID = new ResultID(ResultID.Da.E_WRITEONLY, ResultIDs.E_BADRIGHTS);

    }
    catch (Exception ex)
    {
      output.ID = GetPropertyID(99999);
      output.Description = "Illegal property";
      output.DataType = typeof(string);
      output.ItemPath = null;
      output.ItemName = "Illegal Property";
      output.Value = "Illegal property";
      output.ResultID = ResultID.Da.E_INVALID_PID;
      Tracer.MainTracer.TraceWarning(547, typeof(OpcCom.Interop).ToString(), ex.Message);
    }
    if (deallocate)
    {
      Marshal.DestroyStructure(pInput, typeof(OpcRcw.Da.OPCITEMPROPERTY));
    }
  }

  return output;
}