I was shooting today and when I went to shoot the first frame my 20D gave me an "Error 02" message. Then I hit play and find that the data is corrupted. I had a spare card and used it for the rest of the day. When I got home, I loaded the CF card into my reader just now and I can't access the data at all, says it's corrupted.
The card is an Extreme III 4 GB card rated for 30 mb/s. in the playback menu it said there were 290/290 images, but when I went to format it just now it said it was only using 8.0 KB out of 4GB. I formatted and now the camera and card works fine, took a few shots, all were written and play back fine.
I always format the card in the camera, always eject it properly, etc. Luckily I did not lose any photos because I had just cleared the card a couple of days ago.
Do I trust this card for future purposes or should I ditch it?