Try blowing on the back of the game card, as dust can cause this message, keep trying several times, if you can't get it working then I suggest getting it repaired (if possible). If not buy a new one. At uk.webuy.com (CeX) you can get it the cheapest (as far as I know) however their stock is preowned, if it is not in stock in your local store try on the web or at Amazon.
Hope I helped :D