i only tried 2.57 because it wasn't working at all in 2.58 (again, straight unaltered and add-on packed).  i turned it on just fine, got the Poser Prop Exporter section, but it's empty.  starting it from Terminal, i'm not seeing any errors for Poser Prop Exporter, though i am seeing two statements of it starting up.

"--- Starting Poser Prop Importer Version 9 ---

--- Starting Poser Prop Exporter Version 5 --" 

that's only the one i updated recently.  the one i installed not that long ago just said

"Start Time: 1311523850.675335
PPI.py"

as for the import, the first one i tried that had that simpler error was parts of the Cistern set by Orestes at DAZ.  but trying random other props, items in Ruins of Alecto (DAZ, PC) , Drinking Horns (DAZ, former freebie), and Satin Studio  2 (freebie that i thought was here, but has been replaced by version 3)  also don't work by have an error in the same file at line 1199,  which then refers to line 40 and adjust vert and says that it's not finding a key that seems to relate to the prop geometry (key "[insert name here]" not found).  the only one that worked for me so far was the RDNA Organics freebie props that are very old.  does it only work with props that have embedded geometries?