I got that 404 error too, several times, but apparently the update went ok even though it took longer than usual (because of having to re-try, I imagine).
I'm guessing that at least part of what happened last night was that the program update was right on the heels of a database update, and the servers got swamped with everyone who needed both updates. And Vlk mentioned that one server was down for quite a while, which I'm sure just added to the load on the others.