I think that newer games require higher firmwares. I have a D2Pro (PAL) with Firmware 4.1 (Waninoko's Updater) and no problem with any of the games out there (i can even play US and JAP NTSC Games). Anyway some games require also an update for WiFi (Mario Kart). Without it you can't play online or the game won't work also.
Hope that helps you a bit.