Problem with D90 and memory card

I just received a Nikon D90 yesterday . While using it today, in continuous mode, I have ruined two memory cards. I have no idea why the cards are messing up....I have had no problems with the cards in taking normal pictures. Just when I finish taking a several pics in continuous. When I go to review them, it says the memory card is broken. It will not work in another camera or on my computer. PLEASE HELP!!

That is definitely not right. What brand of memory card? Is it a brand new memory card? Did you format it before you used it? Have you tried formatting it since you had the problem?