the truth - the fonts don't 'protect' from updates. the update screen that displays when updating the dash uses the original MS fonts, being as these are not present in font exploits (i.e UDE, UXE etc) then the update simply crashes. so in a way it sorta offers protection, but not as its intended function. the whole reason of the virtual C was to allow updates and such.
xboxbunny - in future, when reverting to stock, just replace the entire contents of the C drive with the contents of your backup. much easier and will not result in these sorts of errors. is it possible to find out what dash version you have through live or something? all you need is a game/dvd that requires a newer version than the one you are using, that will solve the problem. if by chance you have the latest version, then you will just have to wait for a newer dash to be released then update to that. can i add that if you unplug your xbox from this point on, then you will be forced to open your xbox as the clock will become unset.