windows and Xwindows layout differences

i'm on 2.4, and moving to 2.5 isn't an option just yet ( nore should i
really need to)
and i have this odd problem, under xwindows everything lays out
perfectly. but under windows no matter what i try ReportGrid is always
aligned to the top left. now i have this working on my login screen, the
different is i destroy that panel and create a new one for the ReportPanel.
this is a cut down version i what i do to recreate my problem

def ReportPanel(self, EvtMenu):
    """This creates the panel which allows report options to be specified"""
    self.CurrentPanel.Destroy()

    ReportPanel = wx.Panel(self, -1)
    self.ReportPanel = ReportPanel
    self.CurrentPanel = ReportPanel

    #setup gridbag sizer for information Report layout
    ReportGrid = rcs.RowColSizer()

    ReportGrid.Add(wx.StaticText(ReportPanel, -1, "REPORTS"),
flag=wx.ALIGN_CENTER, pos=(0,1), colspan=5)

    #make panel sizer and layout panel items
    ReportSizer = wx.GridSizer(1,1)
    ReportSizer.Add(ReportGrid,1,wx.EXPAND)
    ReportPanel.SetSizer(ReportSizer)
    ReportPanel.Layout()
    ReportPanel.Fit()