“Card cannot be accessed. Reinsert/change card or format card with camera.”

Sadly, today I found “Card cannot be accessed. Reinsert/change card or format card with camera.”
on my 600D (kiss x5/ t3i), the worse thing is I didn't put the photos to my computcomputer yet and the card cannot be found on my computer. Even try to format in the camera as they show on the screen, it's nor work.
I google it, they said use Photo Recovery Software. But as I said, the card cannot be found in the computer.
I use this card for 2 months, it came with the camera -- the 4 GB Apaccer SD HC card. I hope that this issue
won't happen again with my Kingston card. I don't care the card, but the files.