After looking through your code (and it wasn't easy - please consider formatting it differently next time - maybe grouping the self.sizer.add functions or something) I think I discovered your bug:
When you call Replace on a sizer, the item being replaced is not destroyed but becomes no longer managed by the sizer. You need to hide or destroy the old window (the wx.StaticText)
As mentioned in the wxWidgets docs:
virtual bool Replace (wxWindow *oldwin, wxWindow *newwin, bool recursive=false)
Detaches the given oldwin from the sizer and replaces it with the given newwin.
George Edison
2010-03-26 05:43:06