The URL you posted was not for re-imaging the RoboRIO. This one is for the firmware via the web interface:
http://wpilib.screenstepslive.com/s/...borio-firmware
This one is for the operating system via the imaging tool:
http://wpilib.screenstepslive.com/s/...g-your-roborio
I'm pretty sure you need to do the firmware first. Make sure you don't have a password on your RoboRIO; that will screw up the imaging tool upgrade.