However, I like your alternative workarounds better than my own, and this seems to get round the bug nicely for me:

       action = ""
        while action == "":
            action = poser.DialogSimple.AskMenu("Multiple 'SmartPlusData.txt' files found","Select which to use:",foundfilelist)
            # Handle NoneType return value if Cancel button pressed
            if action:
                locatedfile = action
            else:
               locatedfile = "CANCEL"
            print "TEST RESULT = "+locatedfile

P.S. I don't use wxPython - far too complicated for my decaying brain ! So I'm stuck with PoserPython's built in dialogues

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.

*also available in ShareCG, DAZ, and HiveWire3D flavours (the DeviantArt and CGBytes flavour have been discontinued).