Not much help at the moment but it’s worth doing a full format of your memory card after moving images onto your computer. Because memory cards use the same Fat16 or Fat32 that older versions of Windows use they have an area for marking bad sectors. When you do a full format (that takes about 30 seconds on a 4 gig card) the operating system will mark bad sectors and the camera will not attempt to write to them (I learnt this the hard way). Do this everytime you clear files off a card and you should get fair warning of impeding problems.