Occassionally I've had trouble with my "cheapie" 2 GB SD card from eBay. It turns out that the "lock" switch was sliding freely up and down....sometimes when it should have not been! I ended up using a very thin strip of invisible tape wrapped front to back over the sliding switch to keep it in the "unlocked" position. No problems thus far and the tape does not cause any problems while inserting/ejecting the SD card.