Were you able to use the full capacity of the card before?
Counterfeit memory cards are a huge problem. Often they are much smaller then their stated capacity. Trickery is used to make them appear to be the correct size, but once you start using them you discover the truth - either you can’t use the full capacity or beyond a certain point the data is trashed.
Another useful tool is SD Formatter from the SD Association. But I would use the tool [B]Chef[/B] mentioned first to verify the capacity of the memory card. (IIRC you can change the language to English.)