Border Down
Chaos Field
For some reason my DC has been freezing on me in the middle of gameplay, while playing these particular games. Psyvariar 2 freezes during the 1st stage boss (always at the same spot), Chaos Field sometimes doesn't even get to the 1st stage (the screen stays black right after the ship selection screen), and Border Down freezes on the last level boss, and once in a while on the 1st level boss.
This has been going on just recently. These games were playing great when I first got them. And I know it's not the games themselves, because they are all in mint condition with absolutely no scratches at all. And it can't be my lens because all my other games play perfectly, including my other imports. I think it might have something to do with either my memory card or maybe my gameshark. I went ahead and removed my memory card and it did the trick. All three of the games played all the way through without freezing once. But whenever I have both the memory card and gameshark unit inserted in my controller at the same time, the freezing occurs.

Anyone have any clues as to why this is happening, and why it might have something to do with my memory card?
NOTE: I own one of those 4-in-1 memory cards. I don't have the regular VMU memory cards.
Thanks.