Hello, I had the same problem occur with 2 different memory sticks at the same time. I suspect it was caused by an airport x-ray machine. One of the cards was a Lexar dual-128 Mb card - bank worked fine, the other caused the C:13:01 error on the camera (Sony DSC-P9). At first I tried reformatting the cards through windows - which did not work. However I later found a card format option in the settings of the P9 camera which did the job. Both cards work fine now. If you are still having the problem I hope this helps.