My gf and I got identical flash cards, dsi's and m3i zeros. I set mine up and it worked fine. I showed her how to and watched to make sure that she did everything correctly. Here's the breakdown: My m3 and flashcard work in both dsi's. Her flashcard works in my m3 in both dsi's. Her m3 does not work in either dsi. Her m3 does work in a ds light. Any advice, or should we get in touch with the company that shipped it?