Originally posted by jeantree Will reformatting fix this?
No one can tell. It depends on what caused the probems.
If one of the FATs (File Allocation Tables) is stored in an area which was not detected to be weak by the controller within the SD card, formatting MAY help. This depends of whether the controller will repeatedly write and read (for error detection) during the formatting process. Such details are kept secret by the manufacturers of the cards/controllers, as the controller design makes up for the biggest difference in card performance and reliability.
A single faulty storage bit in a non-FAT area would not cause the symptoms you decribed. Because of the limited number of write processes during life-time of these cards, the controllers try to evenly use all the space on the card. This means, if you delete a file and then store the same file again, it will be on a completely different position of the card.
I myself would format the card in the camera, but I would not expect it to cure the problem.