I've got two identical 16 gigabyte Kingston SD Cards, I shot 900 shots or so over the past week. I picked the camera today and went to shooting and noticed way too many shots remaining on the card. I immediately switched cards.
The card in question only showed about 20 files taken before today.
After googling a bit I used CardRecovery (www.cardrecovery.com)to recover over 1000 files from the presumably corrupt card. As part of the recovery process it scanned the card and didn't find any problems with it.
I do recall an occasion in which the SD card door was open while the camera an XSi was on. Did that cause this? Does it sound like this card is still good?
I guess I'm just gonna make a mark on said card and relegate it to an emergency backup and use the other one and an old 8 gig as primary.