Had loads on my W7 laptop last week and the week before. Almost every day, sometimes several times a day. Not sure what they all were but one 'Security Update' (same number) downloaded and supposedly installed about 5 times.
Not sure whether its the updates or the extra 2gb memory (recycled from my wife's dufunct Laptop) or a combination of both, but its absolutely 'flying' now.
I also had 5 on my Win XP desktop this week as well. Mostly to do with .Net 4.