Odd flicker problem

I have a window with 3 controls on it.  A richedit control, an editbox control, and a listbox control.  None of these controls ever overlap at all.  

While resizing the window, the richedit control, and the listbox control flicker very badly, but the editbox control doesn't flicker at all.  If I remove the listbox control, then nothing flickers when I'm resizing the window.

If I put all 3 controls in the window, and make the listbox control exactly 50 units in height, then nothing flickers when I resize the window.  This is very odd to say the least.

Here is my function which gets called during the WM_SIZING and WM_SIZE messages:

void ResizeControls(HWND hwndChild, RECT *prect)
{
      HWND            hChildCtrl;
      RECT            *r = prect;
      int                  cx, cy;

      cy = r->bottom - r->top;
      cx = r->right - r->left;

      /* Get the handle to the listbox window, and set its new position */
      hChildCtrl = GetDlgItem(hwndChild,IDC_LIST);
      SetWindowPos(hChildCtrl,hwndChild,r->right-r->left-140,5,120,r->bottom-r->top-75,SWP_NOZORDER);

      /* Get the handle to the rich edit window, and set its new position */
      hChildCtrl = GetDlgItem(hwndChild,IDC_RICHEDIT);
      SetWindowPos(hChildCtrl,hwndChild,0,0,cx-160,cy-75,SWP_NOZORDER|SWP_NOMOVE);

      /* Get the handle to the edit window, and set its new position */
      hChildCtrl = GetDlgItem(hwndChild,IDC_EDIT);
      SetWindowPos(hChildCtrl,hwndChild,5,cy - 65,cx-20,25,SWP_NOZORDER);
}