IMPORTANT! What's wrong with my memory card

So I'm using a Nikon D70,
and I was about to upload my pictures when the camera says 'This Card Can't be Used."
I'm freaking out, because this card had important pictures. Things I needed for yearbook class, personals, and projects.
Are my pictures gone?
What's going on?
Can I fix it?
Help!

Added (1). I do upload my pictures daily, which is what I was doing today. However, today I had taken nearly 120 pictures for different reasons, and they are all gone.

This is not important, important is the queen is dead.

There isn't a toggle switch on the side of the card is there? That's the best I can suggest. Sometimes, things just break = \

Indeed it could be that the memory is completely corrupt or just died. It is possible.

I would try to plug the card directly into the computer via usb device, or if you have a card reader. If that does not work, and you really need to get the data, take it to a camera shop or electronic shop.

sadly there's not much you can do

The D70 uses CF cards, so no "locking lever"

First you need to use a USB 2.0 card reader and use your computers file manager to copy all the image files from your memory card.

I have a question.

Why is it you don't copy all your images to your computer at the end of each day of shooting.

The work-flow is usually this

* shoot using a freshly formatted memory card
* at the end of your shooting session, copy the files to your computer
* after you have have verified that all the image files are safely on your computer, format the card using the format feature on your camera.

It is a bad habit to store images on any memory card. Using the delete button to make room for more images on your filling card(s) can lead to card corruption.

If your card reader can't see the images you know are on the card, you will need to buy an image recovery program (about $35 for Lexar Rescue 4)