On my F700 I used the method in this thread to upgrade to 4.01 hybrid.
The install went smooth, it was time to boot back into testmode, but it wouldn't for whatever reason. Perhaps tesmode 2.3 doesn't support 4.0?
The next wall I ran into was it said my old maps were out of date in a window ontop of the splash screen. So I hit OK and it hung on a different spash screen that said Sound.Vision.Soul with the word 'LANGUAGES' at the bottom right of the screen.
I couldn't get past that screen, and after a few min it rebooted on it's own.
So I figured I'd go back and install the orig