Lines in photo

I have a 2 month old Fuji E550, at first the photo's were good, other than outdoor photo's which are continually overexposed no matter what combination I try to solve the bright light issue. After about 250 photo's some began to have lines, striations like finger prints once the images were transferred to the computer or taken to a Kiosk for development. They look fine on the LCD screen. It had been more random, but I just took 80 photo's of my son's 4th birthday and 75 have this problem, it's awful. Don't know what to do, the Fuji site and manual don't mention this problem. Could the xd card have gone bad? Does the camera need some repair? It's new! I have no experience with digital photography, but this is odd. I don't know whether to send it off for repair, or what to do as we have another baby due in a few weeks and I need a camera. I would appreciate any information, if anyone has had a similar issue, or suggestions for something I could be doing incorrectly to cause the problem. Thanks