Yeah, I had to buy a mad-catz memory card for the DC, because I couldn't find a VMU anywhere. I would play NFL2K, and everything would seem fine, then the next time I'd go to play my save file would be lost.

I had simular issues with the vibration pack. I believe it was NFL 2K1 that wouldn't load when I had a vibration pack plugged in, once the game loaded I could insert the vibration pack (Thunder pack) in and play.