Pleased to have found this thread - I was already running v9.2.3, but had tried copying the files from /boot (/flash) on the Raspbian distro and was greatly disappointed.
Reverted my /flash and all is running great, booting from USB flash drive.
Just thinking - a long time ago, when I was running OpenElec on Intel hardware, I was using network boot - perhaps I can try that again.
Did you replace files on the usb stick?