Fujifilm xd picture card problem. i have had my fujifilm finepix F470 for a while now but

Question

i have had my fujifilm finepix F470 for a while now but yesterday i took my card out to download photo's put it back in the camera and it says card not initialized, put it in my computer and it says the same, what has happened please and how can i solve this as i still have very important photo's i would be gutted to lose, thanks