A:  You declare the parameter on the Delphi side as an open array, but it isn't one! An open array parameter in Delphi consists of a pointer to the array data and an additional word that gives the actual size of the passed array, 6 bytes in total. What VB provides is only the pointer to the data, so you have a mismatch in parameter list sizes, which is a sure recipe for GPF.

Try this one, modified from your code:

' Start of VB Code ****************************************
' Form level declarations
Declare Function ReadArray Lib "TestDLL.dll" (TestArr As Any, ByVal Size as
Integer) As Integer

Dim TestArray(3) As Integer  ' Declares an array[0..3] of integer in VB

Sub Form_Load

  TestArray(0) = 2
  TestArray(1) = 4
  TestArray(2) = 6
  TestArray(3) = 8

End Sub

Sub cmdDelphi_Click ()
Dim iResult As Integer

  iResult = ReadArray(TestArray(0), 4)  ' Documentation says this is the way
to get VB to
                                     ' pass a pointer to an array
  MsgBox "Back once again with result = " & iResult

End Sub
' End of VB Code  ********************************************

Code in Delphi is:
{Start of Delphi Code ****************************************}
interface
.
.
Type
  TIntArray = Array [1..High(Word) div Sizeof(Integer)] of Integer;
function ReadArray(var TestArray: TIntArray; size: Integer): integer; export;
.
.

implementation

function ReadArray;
var
  iCount : integer;
begin

  for iCount := 1 to size do
  begin
    ShowMessage( 'Element ' + InttoStr(iCount) + ' = ' +
IntToStr(TestArray[iCount]));
  end;
  Result := 4;
end;
{End of Delphi Code ****************************************}