Thanks for the link, jbamberg. That worked and now have the new update! I tried loading my sessions at random, and no crashes, which was a problem before. I'll check the scenes next. I know that was part of the update, so I'm sure those will go smoothly too, now.
No I've not got internet sharing enabled–only "cache Icloud content" is activated on the sharing on my mac.
It's good to hear you could update successfully using the USB installer.
If you are using one of the Mac Pro's ethernet ports for your H9000, and the other one is connected to your switch or router, you might need to enable internet sharing for the H9000 to be able to use the Mac's internet connection for updating. If you don't want the H9000 to be connected to the internet normally, you could just enable it when you want to update, and turn it off otherwise.