I have a very simple COM-add-in where I try to access a folder.
But the direct access by index fails:

CComPtrOutlook::_NameSpace NameSpace;
m_spApp-GetNamespace(L"MAPI", &NameSpace);

CComPtrOutlook::MAPIFolder InBoxFolder;
CComPtrOutlook::MAPIFolder RootFolder;
NameSpace-GetDefaultFolder(Outlook:lFolderInbox, &InBoxFolder);
InBoxFolder-get_Parent((IDispatch **)&RootFolder);
CComPtrOutlook::_Folders Folders;
RootFolder-get_Folders(&Folders);

Outlook::MAPIFolder * pFolder = NULL;
HRESULT hr = Folders-GetFirst(&pFolder);
ATLASSERT(hr == S_OK);
hr = Folders-Item(CComVariant(0), &pFolder);
ATLASSERT(hr == S_OK);

The second ATLASSERT() fails (out of bounds) whereas the first succeeds! Why?