Three words - format, format, format.

I've never heard anything else. When you format, you re-install (correct term?) the directory of the card which can have a lot to do with avoiding lost images. I do it and have never had a problem, bottom line.

I also re-format only in the camera (not on computer), and only after I'm ready to shoot on that card again. Reason being, I save to the hard drive and then burn to a CD. If something happens during the transfer or I accidently save an edited image before I get a chance to burn a CD, then I have a backup still on the card for a couple days (or until I use it again).