Won't take pictures

Every time something strange happens to a camera, switch it of and on again. Of one step up. Remover the battery and reinsert it. Next step is to remove both the battery and the memory card. And when you are there, please check if nothing is wrong with the memory card and its contacts. Only a spec of dust in the camera, on one of the contacts, could split the fun.
Check is all contacts (Memory card and battery, and also the ones in the camera) are clean and shiny. Special the contacts on the memory card should be not bent or have a dent.
Try to rescue the pictures on the card to your computer, and when it is in the memory card reader, format the card, with FAT32.
If the card has any defect, your computer will tell you.
If after trying everything here, does not change the situation, please visit your dealer or a certified repair centre. (or start saving for a new camera.
CLEANING of contacts only use a dry cloth or cotton swabs. Never use anything sharp in or close to a camera.

To make sure the card is formatted correct, do a format in the camera. I'm not sure if the newest UDMA CF cards are compatible with your camera. But I think you still have an old card, you can format. Please also check all contacts in the camera are still straight. Us a bright light and a magnifying glass.
Also take time to check your battery is still good. I'm sure you have more than one. Also check the battery contacts, if they ate clean and shiny. Only to be cleaned with a dry cloth or cordon swabs.
When you removed the battery, you already did a reset.
Till now I can't think of more to help you.

Success

I love my Nikon

You can replace the contacts, but a light scratch would not cause a lens communication error. Using your fingernail, push all the contact pins in the mirror box in and out 5-6 times to break any corrossion between the pins and their ciruit board

Try taking out memory chip, don't touch the gold fingers, and insert it into your computer. Should read it as if it were a thumb drive, then open, drag and drop into a file.
Also chip might need to be re formatted, last resort though.
Had a case where the card just needed to be taken out of camera and put back in to clean contacts.

If there is no light in the little light above the LCD.
Here are the steps:
1. Make sure you will install a new or fully charged battery/batteries into your camera. Please use lithium batteries Ni-Mh or rechargeable Batteries (2000 M.Amp or higher).
2. Clean the battery contacts.
a. Remove the battery/batteries and the memory card from your camera, then wipe the battery contacts with a soft, clean cloth.
b. Reinstall the battery/batteries into your camera
3. Turn on your camera without the memory card.

If there is a light in the little lamp above the LCD.
You will need to order your repair or Trade up please Contact KODAK:
http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=14563&pq-locale=en_US&_requestid=3490

Try cleaning the battery contacts inside the camera with a cotton swab lightly dampened with rubbing alcohol.

Err 99 usually means your lens contacts are dirty either on the lens itself or on the camera.

To isolate the cause of the issue, do the following: -
1. Turn off the camera.
2. Remove the lens, battery, and CF card.
3. Allow the camera to sit without power for approximately 20 minutes.
4. Insert only a fully charged battery, and turn on the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, the camera may be faulty and requires a service. If it does not, then: -
1. Turn off the camera.
2. Insert the CF card.
3. Turn on the camera.
4. Format the CF card in the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, then the CF card is faulty. Try a different card. If the message does not appear: -
1. Turn off the camera.
2. Clean the gold contacts on the lens by GENTLY rubbing them with a pencil eraser or soft cloth. Keeping the camera face pointing down, also clean the gold contacts on the camera, being careful that you do not let any debris fall into the camera body.
3. Reattach your lens.
4. Turn on the camera.
5. Depress the shutter button as you would to take a picture.

If the “ERR 99" message only appears when one particular lens is attached, then that lens should be examined by a service technician.
If you see the “ERR 99" with a different Canon lens attached, then the camera is faulty and should be serviced.

the lens contacts are probably dirty so,

1. Get a pencil with an eraser on the end, Detach the lens from the camera, hold it so that the lens’ gold contacts are pointing down and lightly erase their exposed surface, cleaning them of anything that may have coated them making the contact poor.Lightly dust the contacts with a small paintbrush to remove any loose dirt.
   
2. Do the same thing with the gold contacts inside the camera body. This is a little more difficult.: just hold camera so lens opening points down so no gunk falls in. Erase lightly.Use a lens cloth or paint brush to remove dirt.
3. PLEASE REMEMBER TO KEEP THE CAMERA POINTING DOWN, AND THE SAME WITH THE LENSES AND O0NLY GENTLY RUB THE CONTACTS TO PREVENT DIRT INGRESS INTO THE CAMERA OR LENS
   

If two cameras are doing it, I would suggest the contacts on your lens are dirty.

Try the following diagnosis steps for solving ERR 99 issues : -

To isolate the cause of the issue, do the following: -
1. Turn off the camera.
2. Remove the lens, battery, and CF card.
3. Allow the camera to sit without power for approximately 20 minutes.
4. Insert only a fully charged battery, and turn on the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, the camera may be faulty and requires a service. If it does not, then: -
1. Turn off the camera.
2. Insert the CF card.
3. Turn on the camera.
4. Format the CF card in the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, then the CF card is faulty. Try a different card. If the message does not appear: -
1. Turn off the camera.
2. Clean the gold contacts on the lens by GENTLY rubbing them with a pencil eraser or soft cloth. Keeping the camera face pointing down, also clean the gold contacts on the camera, being careful that you do not let any debris fall into the camera body.
3. Reattach your lens.
4. Turn on the camera.
5. Depress the shutter button as you would to take a picture.

If the “ERR 99" message only appears when one particular lens is attached, then that lens should be examined by a service technician.
If you see the “ERR 99" with a different Canon lens attached, then the camera is faulty and should be serviced.

Try the following diagnosis steps: -

To isolate the cause of the issue, do the following: -
1. Turn off the camera.
2. Remove the lens, battery, and CF card.
3. Allow the camera to sit without power for approximately 20 minutes.
4. Insert only a fully charged battery, and turn on the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, the camera may be faulty and requires a service. If it does not, then: -
1. Turn off the camera.
2. Insert the CF card.
3. Turn on the camera.
4. Format the CF card in the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, then the CF card is faulty. Try a different card. If the message does not appear: -
1. Turn off the camera.
2. Clean the gold contacts on the lens by GENTLY rubbing them with a pencil eraser or soft cloth. Keeping the camera face pointing down, also clean the gold contacts on the camera, being careful that you do not let any debris fall into the camera body.
3. Reattach your lens.
4. Turn on the camera.
5. Depress the shutter button as you would to take a picture.

If the “ERR 99" message only appears when one particular lens is attached, then that lens should be examined by a service technician.
If you see the “ERR 99" with a different Canon lens attached, then the camera is faulty and should be serviced.