Its a very common problem with S400,S410 and some others.
As a case study, see the following error message on the Canon IXUS 130 when trying to view some photos previously stored in the memory card SDHC
"Memory Card Error"
Every single photo stored on the memory card becomes inaccessible after the above error message. In addition, no more photos can be stored on the memory card. In short, the card can not be read or written.
The above error message that makes all the pictures inaccessible is mainly caused due to corruption of the memory card. Reasons why you are responsible for the above error message is virus infection, interrupted read / write operation, and human error.
The resolution for the above error message is the format of memory card into the camera. The process erases all data previously stored and allows you to save the new data. While the format is a good resolution for users who do not require the old data, it is fatal to users such as photographers, detective agencies, etc, to save critical data on your memory card. However, the formatted data recovery day is now an easy process. It is therefore necessary to use an advanced part of third parties. A tool for image recovery is readily available on the Internet by one click.
Data Recovery is an application of high-end recovery that recovers data from almost all formats SDHC Card, XD and MMC. The read-only photo recovery tool also allows you to restore data in the defined location. The software runs on Mac OS X and Windows.
Check this link for additional details: Simple Fixes for SD "Memory Card Locked" or "Memory Card Error"