Guess what - magnets can't ruin your SD cards. Let's just get that one out in the open. Flash memory just doesn't work that way! I mean, magnets could work, but it would have to be really, really powerful. Nothing that you have in your household would ruin one, for the record. So yeah, let's just dispel that myth. However, there are a variety of reasons that you can't your SD card, and it seems as though nearly everyone faces the same issues.