First time got a wired TF-Card problem

After a flight, I want to download logs, but all logs=0kb from the GCS I can see, so cant download anything! Then I pulled the Card out and read it on PC, there were .bin files in Card, and the data is right! Anybody got this wired problem before? And what can cause this problem?
Then I format the Card and have another flight, there is no problem anymore!