Let me clear up a few things. First, I use NIKON approved LEXAR Cards, and that is not the problem. I got all the photos back since I purchased a Card Reader. So the cards are not the problem. I shut my camera off when I swap out cards, that is just common sense and I follow the instructions closely. On the D800 the SD Card was not affected as I was able to talke photos and copy from SD, its the CF side that states its a bad card. Tried several KNOWN GOOD cards and even different brands (SCANDISK) and same results. So both cameras on why to NIKON for service. This is a real brain teaser.

SkintBrit said:
...and.........NOTHING! frightened the living daylights out of me

Another heart stopping trick

Using the D800, write to the SD card, then, thinking it's the D700, try to down load the non existent RAW files on the Flash card

You have made sure that you haven't put the D700 formatted card in the D800 haven't you? This nearly gave me a coronary one time, when after a wedding I got home and my wife wanted to look at some of the shots. I put a card in the camera and.........NOTHING! frightened the living daylights out of me till I scratched my head and it finally dawned on me what I'd done. You've probably sorted the problem now, but I'd be willing to bet there is/was nothing wrong with your cameras?

Just for you info, there are various types of SD cards on the market.

For example, the same company (I don't want to say its name, but it is a well know company that does memory chips) have different flavors of the same SD card, there are those that can be used for "critical" devices that may be able to keep the information correctly even after 100K write times, others that typically last only around 2K (two thousand) writes, while the commercial/cheap ones may only last up to 200 write times.

The "write times" is the number of times you can fill all the SD card and then erase it.

This is governed by the number of "bits" every memory cell stores in the SD Card. The SD Card controller (That works transparently inside the SD Card when you read/write info from it) is the one that will keep order on the card, that is, it will be moving new info to unused cells, allowing much more than the announced number or full writes.

This even gives more reasons why not to fill up the whole card when you take photos and follow the rules Adamz mentioned below:

adamz said:I personally don't like to put more than 300-400 pics on a single card, due to a possible card failure (and if shooting jpg's only I'm backup to second slot). anyway, what's done is done and in this case I'll go with spraynpray's advice and used the sandisk recovery software.

I easily fill up a card with that amount during an air show, but I do download them to my computer ASAP :)

Ebvette may have altered the cards when he watched the pictures on his computer with the cards in a card reader and, for instance, deleted some of them. I did that once a long time ago. Only once because I learned a good lesson then !

spraynpray said:
1300 images is waaaay too many to have on one card BTW - guess why?

What Adamz said. ebvette has illustrated the problem - waaaay too many eggs in one basket.

@PB PM - it is way to much - I personally don't like to put more than 300-400 pics on a single card, due to a possible card failure (and if shooting jpg's only I'm backup to second slot). anyway, what's done is done and in this case I'll go with spraynpray's advice and used the sandisk recovery software.

@ebvette - it's highly unusual that both cameras doesn't accept cards, please either borrow a working card from Your friend and check either it works. if it will work (which I'm 99% sure) it means that Your cards are corrupted and that can mean that there's a device at Your side that damages them - I would look at card reader as a possible fault device.

How is 1300 too many, what if the OP is shooting JPEG?

Sounds like you may have 'hot swapped' your memory cards (pulled them out/inserted them without switching the printer off) - they don't like that. Try downloading the rescue program from Scandisk and running it to rescue your images. I am sure the images are there, your cameras just can't see them.

What happens if you format the cards in camera?

1300 images is waaaay too many to have on one card BTW - guess why?

On both my D700 and D800 all of a sudden both cameras will not read any of my memory cards, all come up with error, "Memory Card is Damaged CANNOT be Used" Yet on my HP printer I can see the pictures of the memory cards, but my camera no matter what card I put in now go to Memory Failure. Can I resets the camera like a Hard Boot or what...???? Both D700 and D800 will not except any memory cards. FYI using in the 800 NEW Lexar Proffesional 400X 16M. Took 1300 Photos on one and it download fine, and about 1300 photos on the second, and that one kept failing to download. Even now when I go back to the one that Downloaded successful it shows errors. Even if I use different manufacturs cards they all fail now. HELP>>>>