C90LE7 - boot error after updating with USB Firmware Tool

I have been trying to update a C90LE7 to the latest firmware using the USB Firmware Tool, but even though it appears to complete the update successfully, when I remove the USB and the device restarts is encounters a boot error ('Unable to read boot configuration data').

I have tried both version 1.13 and 1.15 of the USB Firmware tool, but am getting the same error on restart.

It also doesn't appear to be the USB sticks themselves, as the firmware tool completes ok.

Is there something i am missing?