One of the first things an update does is check the phone's "signature" (each manufacturer uses a different way of doing it, but basically it checks to make sure that you're running the stock ROM, not something like Cyanogen). Then it checks for root. If eiher of those checks fail, the update is supposed to stop, because updating a custom ROM or a rooted stock ROM with a stock update could brick the phone.
It should have "failed" before it actually did anything. Evidently it did something before it failed - and caused a problem.
Bring it to your carrier and see if they can reflash the update or, barring that, the whole ROM (you'll lose any data on the phone if they have to do that).