Nikon Coolpix-doesnt recognize SD -plz help

This was a great camera - Nikon Coolpix s51- after using for about a yr. i changed memory cards from a sd 128mb to a SD 2 gb which is worked for awhile. When i took the card out loaded into the computer and removed the photos I put the card bk in and the camera doesnt recognize the card is there (it gives no error reading) but says i can only take 5 photos which are recorded to the camera itself not the card. I have formatted the card - put the other card bk in - it gives me the same results. Says I have 5 photos that can b taken. i have taken both cards and placed them in another digital camera and they work fine. They work fine when they loaded into the computer - no problems there. I am so frustrated - have tried over & over to search the internet for results, I feel like I didnt get enough use out of the camera for the price I paid for it. Anyone with any suggestions please help me. Thanks in advance for your time