My Playstation 2 memory card doesn't work anymore?

So I accidently took out my memory card to play Guitar Hero Aerosmith one day, but put it back in once I realized my mistake. I almost never take it out. Heck, for two years I don't know if I ever did since I got it. I usually always play Madden, so when I tried to play Madden 11, I keep getting an error message saying 'Error reading memory card. The memory card has been either removed or replaced.' I have tried blowing as hard as possible into the memory card and the part where you put the card in. To no avail. Nothing is rattling inside it. I have scoured Google for an answer but haven't gotten one. What should I do to fix this problem? It says there is no data on the card, but it senses one there when I go to browser. I have a slim.