Just came here to mention that I was able to complete the firmware update normally through iCue, without encountering an error, by going into Safe Mode with Networking. Did it a couple months ago and it's been fine since, aside from the typical intermittent profile loading errors on launch (which occurred before as well and are more than likely related to iCue rather than the keyboard itself).
Might be worth a shot for anyone who hasn't tried.
Cheers to Corsair Calico Jack for this solution.