couldnt get it to work on my retail either, usually when you replace your gpd with another one, you need the game save file that goes with it for it to work, i've had the same problem with other gps'd got the save file that goes with it and it usually worked
I don't think the GPD itself works without actually being linked to your profile. I believe it is the same for a lot of games. Maybe an actually editor would do the trick?