Was the speedtest done wired, wireless or homeplugs? At a sync of 39992 I would guess that you would have a profile of 38717 down. I Could not use the BT speedtest the first day I was connected to Infinity, so you are probably correct in that it is the system updating.
BT -> Zen -> F2S -> Bulldog -> Be* -> BT Infinity
Far too many computers, 1 Wife, 3 Maine Coons and too many horses