Formmatted memory card showing check card
You don't state the type nor capacity of card you're attempting to use, but the problem you describe is typical of having used the wrong one.
Your SV-AV50 is compatible with SD cards only up to an absolute maximum capacity of 2GB. I strongly suspect that you have tried to use an SDHC card which will fit in the slot and looks the same, but as a later development it's incompatible with all hardware designed for regular SD cards only..
Your camera cannot be updated to use SDHC cards, so if my guess is correct then your fix is to use the correct card type.
Another possible cause is if you have formatted the card via your computer. You must never do this, always re-format in the camera only. If that's what you have done then with a fully charged battery try to re-format the card in your camera, but sometimes this doesn't work and the card cannot be used in the camera again.
The final causes are that either the card has failed or that the camera has failed. The first can be fixed by replacing the card (many major brand names will replace them even if the warranty has expired), the latter is not a DIY fix and the camera would need a professional repair, but you can buy brand new, no-name, basic models of similar or better specification for far less than the repair costs to yours.