CListView/CListCtrl insertion not at proper index

Hi,
I have a SDI application in which one of the panes is CListView derived.
The list view is in report mode
I am inserting the items in the list but some items doesn't get inserted
in the position I am inserting.

I have over-ridden the create member of the CListView like this

BOOL CMyListView::Create(LPCTSTR lpszClassName, LPCTSTR lpszWindowName,
DWORD dwStyle, const RECT& rect, CWnd* pParentWnd, UINT nID,
CCreateContext* pContext)
{
    dwStyle ^=LVS_SORTASCENDING;
    dwStyle ^=LVS_SORTDESCENDING ;
    dwStyle|=LVS_EX_FULLROWSELECT| LVS_REPORT|LVS_ICON ;

    return CWnd::Create(lpszClassName, lpszWindowName, dwStyle, rect,
pParentWnd, nID, pContext);
}

and I am inserting the items like

    LVITEM item;
    memset(&item,0,sizeof(item));
    item.mask = LVIF_TEXT |LVIF_PARAM | LVIF_IMAGE;
    item.iItem = iPos;
    item.iImage = -1;
    item.lParam = lTAG;
    item.pszText = (LPTSTR)szItemText;

    int nPos = GetListCtrl().InsertItem(&item);

the value of iPos starts at 0 and increments for subsequent items and
then inserting the subitems using SetItemText. I have also tried passing
0 for item.iItem for all items. In either case the items should be
inserted either at top or end of the list, but some items goes and anywhere.

What could be the reason for the item not getting inserted at the
requested index?

Thanks & Regards
Ashutosh