Hello Robin,
Please distill it down to a complete sample that shows the problem.
----------------------------snip------------------------------------
#!/usr/bin/env python
from wxPython.wx import *
from wxPython.wizard import *
app = wxPySimpleApp()
wizard = wxWizard(None, -1, "Just A Wizard")
page1 = wxWizardPageSimple(wizard)
txt = wxStaticText(page1, -1, "Hello Wizard")
vals = ['foo', 'bar']
page2 = wxWizardPageSimple(wizard)
lb = wxListBox(page2, -1, choices = vals)
wxWizardPageSimple_Chain(page1, page2)
wizard.FitToPage(page1)
# starting on page1, switching to page2 results in an empty
# listbox
wizard.RunWizard(page1)
# starting on page2 shows the listbox with values...
# wizard.RunWizard(page2)
wizard.Destroy()
app.MainLoop()
----------------------------snap------------------------------------