Same SD card problem with Dimage Z5
Your Card may need to be formatted. to fix this problem:
[note- before you start, make sure that your SD Card is blank, or that the information is unimportant, because formatting your card will erase all of the information.]
1) Plug the card into your computer, if you can, in the SD slot, or use a USB - SD transformer to plug your card into a USB port.
2) After its plugged in, go to 'My Computer'.
3) Right Click on the drive its plugged it into
4) press format
5) Make sure all of the correct settings are on and start the format.
now your SD card is formatted and should work in your camera and you can continue taking pictures. YEA :^)