I had the same problem. It is the contacts in your Olympus. I tried this and it worked like a charm. I slid a piece of paper in with the card, on the opposite side from the contacts. This pushed the card over a few thousandths of an inch and the card made contact with the contacts, and the card worked. I left the paper in for a week or so and when I removed the card (and paper) to dump it onto my PC I neglected to put the paper back with it, but . . . it worked and has worked ever since. I guess the extra pressure applied to the contacts must have cleaned them. Now I can use any of my cards in the camera without the paper. One would think Olympus would supply some sort to contact cleaning card with a very fine abrasive on it to clean the contacts, or maybe it makes better business sense to them to not fix the problem and to sell more cameras!!
Bob