Checked some of the scripts that come with Poser6 and found these variants which both work:

getOpenFile = poser.DialogFileChooser(type=poser.kDialogFileChooserOpen, message="Dialog title text goes here", startDir="nothing");

getOpenFile = poser.DialogFileChooser(type=poser.kDialogFileChooserOpen, message="Dialog title text goes here");

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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).