Did you power off the unit after the update. If yes, did you tried to start the update process again by pressing In/cue and Reloop/exit button while power on the unit?
If you do so, you should reformat the USB drive and load a fresh copy of the update file.
If you haven't powered off the unit after the failed update and are hesitent to do so, you should wait for Pioneer DJ to respond. Not sure if it is save to power it off in this state.