Exactly how do you know they are gone?
Do they show on your PC?
Do they show in Files on your Archos?
This has happened several times but the most recent was this afternoon.
I copied 60 jpg files to a folder on the SD card then browsed through them in the gallery. I added 4 more files a few hours later. I went back to the gallery and it only showed 4 files. The file manager on the A70 showed the same thing. Connecting with the USB cable and browsing from the PC also showed 4 files.
I ran Recuva on the SD card and recovered about 50 of the original files. It said it recovered all of them but some were corrupted.
I haven't actually lost anything but some time since all the photos are saved on my PC anyway.
I ran h2testw and it wrote and verified 16gb twice with no errors. I did the full, slow reformat of the card before running h2testw. Maybe that was all the card needed.
The card didn't come from Ebay but from a retailer that I've bought a dozen or so memory cards from and never had a problem.
I think this had something to do with the Froyo update. All of my photos disappeared from the SD card when I updated. The funny thing is that the directory structure and all of the Word docs stayed on the card. Only jpg files were deleted.
I backed the card up before updating to Froyo and I just copied all the photos back to the card. I'll add some more files tomorrow and see what happens.