Blurred Photos

Hi, I've had my new D5100 a couple of weeks now and I'm testing it out. Previously I owned a D3100 and had spectacular results. I knew my way around the camera and its settings, however all the shots I have taken with the D5100 with 18-55mm and 55-200mm lens have been really disappointing. Sometimes when out shooting I will get random blurred shots even though camera says all in focus, and many of the shots when viewed back on the PC lack focus and sharpness. Do you think it's possible I have a duff camera ? Any other ideas if I am doing something very wrong?