Is your memory failing? It could be your age, or it could be you've bought counterfeit memory!
If you've bought a memory device, mp3 player, usb stick or a card for a phone or camera it could be fake.
So how do you know? well, the only way is to test it, just because your device recognizes a card as say 16GB the card could have been hacked to show as 16GB when in truth it's only 1GB, your evice won't know this and will keep writing to the card until it reaches said 16GB, unfortunately 15GB of that will be corrupted an lost forever.
So what to do? As soon as you receive your memory run a test I recommend H2testw a tiny program that writes data to your card then reads it and tells you what just happened, for example, test a 16GB card and 2GB comes back good 14GB comes back as defective, this proves you've just bought a 2GB masquerading as a 16GB.
Always report this to ebay, inform the seller and demand a full refund, once you have received your money back (hopefully) leave negative, but honest, feedback such as
Negative - Fake memory supplied-true capacity ??gb BEWARE.
Ebay is awash with these fakes, be aware and together we can stamp them out!!