Hi! I have the same problem - one of my SD cards died in 802w... And some other man from our russian forum 4pda also had such problem.
My idea of what happens is that it's just the mechanical damage. There are some projections on the inside of the back cover which are supposed to hold SD and SIM cards in place so they don't slip out of slot (?), but the problem is they're placed too close to the slot's end. So if you close the back cover that projection may press on SD card's end and just cracks it in two pieces.
At least that's what happened with my microSD... First I didn't notice it but then checked and it's really cracked. So this may be an answer - careful people tell that cards work normally, and strong people like us [
] experience dead cards...