The API function GetOpenFileName does not work in Excel 2010, but works in Excel 2007

The function GetOpenFileName does not work in Excel 2010 (32 bit) in Windows 7, but does work in Excel 2007 (32bit) in Windows. The window does not open and returns "false" to Output. To test the code, you need to run the sub startit.
The problem happens in thCommonFileOpenSave, Line containing "If OpenFile Then fResult = th_apiGetOpenFileName(OFN) Else fResult = th_apiGetSaveFileName(OFN)"

Code:

Option Explicit

Type thOPENFILENAME
lStructSize As Long
hwndOwner As Long
hInstance As Long
strFilter As String
strCustomFilter As String
nMaxCustFilter As String
nFilterIndex As Long
strFile As String
nMaxFile As Long
strFileTitle As String
nMaxFileTitle As Long
strInitialDir As String
strTitle As String
Flags As Long
nFileOffset As Integer
nFileExtension As Integer
strDefExt As String
lCustData As Long
lpfnHook As Long
lpTemplateName As String
End Type

Declare Function th_apiGetOpenFileName Lib "comdlg32.dll" Alias "GetOpenFileNameA" (OFN As thOPENFILENAME) As Boolean
Declare Function th_apiGetSaveFileName Lib "comdlg32.dll" Alias "GetSaveFileNameA" (OFN As thOPENFILENAME) As Boolean
Declare Function CommDlgExtendetError Lib "commdlg32.dll" () As Long

Private Const thOFN_READONLY = &H1
Private Const thOFN_OVERWRITEPROMPT = &H2
Private Const thOFN_HIDEREADONLY = &H4
Private Const thOFN_NOCHANGEDIR = &H8
Private Const thOFN_SHOWHELP = &H10
Private Const thOFN_NOVALIDATE = &H100
Private Const thOFN_ALLOWMULTISELECT = &H200
Private Const thOFN_EXTENSIONDIFFERENT = &H400
Private Const thOFN_PATHMUSTEXIST = &H800
Private Const thOFN_FILEMUSTEXIST = &H1000
Private Const thOFN_CREATEPROMPT = &H2000
Private Const thOFN_SHAREWARE = &H4000
Private Const thOFN_NOREADONLYRETURN = &H8000
Private Const thOFN_NOTESTFILECREATE = &H10000
Private Const thOFN_NONETWORKBUTTON = &H20000
Private Const thOFN_NOLONGGAMES = &H40000
Private Const thOFN_EXPLORER = &H80000
Private Const thOFN_NODEREFERENCELINKS = &H100000
Private Const thOFN_LONGNAMES = &H200000

Function StartIt()
Dim strFilter As String
Dim Output As String
Dim lngFlags As Long
strFilter = thAddFilterItem(strFilter, "Excel Files (*.xls)", "*.XLS")
strFilter = thAddFilterItem(strFilter, "Text Files(*.txt)", "*.TXT")
strFilter = thAddFilterItem(strFilter, "All Files (*.*)", "*.*")
Output = thCommonFileOpenSave(InitialDir:="C:\Windows", Filter:=strFilter, FilterIndex:=3, Flags:=lngFlags, DialogTitle:="File Browser")
Debug.Print Hex(lngFlags)
End Function

Function GetOpenFile(Optional varDirectory As Variant, Optional varTitleForDialog As Variant) As Variant
Dim strFilter As String
Dim lngFlags As Long
Dim varFileName As Variant
lngFlags = thOFN_FILEMUSTEXIST Or thOFN_HIDEREADONLY Or thOFN_NOCHANGEDIR

If IsMissing(varDirectory) Then varDirectory = ""

If IsMissing(varTitleForDialog) Then varTitleForDialog = ""

strFilter = thAddFilterItem(strFilter, "Excel (*.xls)", "*.XLS")
varFileName = thCommonFileOpenSave(OpenFile:=True, InitialDir:=varDirectory, Filter:=strFilter, Flags:=lngFlags, DialogTitle:=varTitleForDialog)

If Not IsNull(varFileName) Then varFileName = TrimNull(varFileName)

GetOpenFile = varFileName

End Function

Function thCommonFileOpenSave(Optional ByRef Flags As Variant, Optional ByVal InitialDir As Variant, Optional ByVal Filter As Variant, _
Optional ByVal FilterIndex As Variant, Optional ByVal DefaultEx As Variant, Optional ByVal fileName As Variant, _
Optional ByVal DialogTitle As Variant, Optional ByVal hwnd As Variant, Optional ByVal OpenFile As Variant) As Variant

Dim OFN As thOPENFILENAME
Dim strFileName As String
Dim FileTitle As String
Dim fResult As Boolean

If IsMissing(InitialDir) Then InitialDir = CurDir
If IsMissing(Filter) Then Filter = ""
If IsMissing(FilterIndex) Then FilterIndex = 1
If IsMissing(Flags) Then Flags = 0&
If IsMissing(DefaultEx) Then DefaultEx = ""
If IsMissing(fileName) Then fileName = ""
If IsMissing(DialogTitle) Then DialogTitle = ""
If IsMissing(hwnd) Then hwnd = 0
If IsMissing(OpenFile) Then OpenFile = True

strFileName = Left(fileName & String(256, 0), 256)
FileTitle = String(256, 0)

With OFN
.lStructSize = Len(OFN)
.hwndOwner = hwnd
.strFilter = Filter
.nFilterIndex = FilterIndex
.strFile = strFileName
.nMaxFile = Len(strFileName)
.strFileTitle = FileTitle
.nMaxFileTitle = Len(FileTitle)
.strTitle = DialogTitle
.Flags = Flags
.strDefExt = DefaultEx
.strInitialDir = InitialDir
.hInstance = 0
.lpfnHook = 0
.strCustomFilter = String(255, 0)
.nMaxCustFilter = 255
End With

If OpenFile Then fResult = th_apiGetOpenFileName(OFN) Else fResult = th_apiGetSaveFileName(OFN)


If fResult Then
If Not IsMissing(Flags) Then Flags = OFN.Flags
thCommonFileOpenSave = TrimNull(OFN.strFile)
Else
thCommonFileOpenSave = vbNullString
End If

End Function

Function thAddFilterItem(strFilter As String, strDescription As String, Optional varItem As Variant) As String

If IsMissing(varItem) Then varItem = "*.*"
thAddFilterItem = strFilter & strDescription & vbNullChar & varItem & vbNullChar

End Function

Private Function TrimNull(ByVal strItem As String) As String
Dim intPos As Integer
intPos = InStr(strItem, vbNullChar)
If intPos > 0 Then
TrimNull = Left(strItem, intPos - 1)
Else
TrimNull = strItem
End If

End Function