ahhh, I think I know what it is. I've chosen "Friend Of The Night" perk, and it is turning the streetlamps from specs of light to actual streetlamps that actually illuminate the area underneath them. Cool
Do they look like this?
http://crimsonkeep.com/wallpapers/data/media/33/streetlight1.jpg
http://crimsonkeep.com/wallpapers/data/media/33/streetlight2.jpg
Cause if so, it's not Friend of the Night. That's what I've seen in my game without that Perks/mods for a long time.
Maybe you had a minor bug that kept them from working properly (graphic driver/bloom/hdr issue or game itself, who knows) and the patch made it go away.