May be its just that the raspbian-image was not written correctly onto the sd-card. I experienced this on my own last week, when I was writing an image to an sd-card while doing lots of other usb-related stuff on the usb-hub where my card-reader was attached to. I just rewrote the image to the sd-card and everything was fine.
Before returning your RaspberrPi download the lasted raspbian image and try to rewrite it to your sd-card. http://www.raspberrypi.org/downloads
If that doesn't work try to write the raspbian-image to another sd-card.
It is also possible, that you have a power-problem, when I started my RaspberryPi for the first time I got tons of errors of all kind, they all went away after I replaced my power-supply (and / or micro-usb-cable, it's unbelievable how bad many of this cables can be).