Why won't my camera read my memory card?

I have a Nikon S4000 and I'm using a Lexar platinum II 8gb sdhc 100x card. When I take a video it records for maybe 5 seconds then stops and reads "This card can't be read." Formatting fixes it, but only for a while until it happens again. Is anyone using this camera and uses a card that isn't having any problems? Please leave suggestions.

The card is too slow. You need some class 10 cards. They're about the only card out there that will record video fast enough to keep up with the huge data stream it develops. Class 10 is the fastest card currently available. On my t1i video is recorded almost before I know it's happening.
8gb / Class 10 = $25 each.

Wow, Jim? Does the card record before you press the button? Wow!

Katie, listen to Jim. He knows videos. Your existing card can't keep up with the camera. You need a faster card. A much faster one.