Google is broke. I got a link from Washington post a couple of days ago on a three week old site, and analytics messes up on me. That place is ridiculous. And about the same time my adsense earnings just plummett. Tons of clicks (five times what I started with)and money gets halved. Man I gotta get off the google crack.
Got three G analytics accounts and all of 'em are showing a break around mid day february first - my heart skipped a beat there for a second too but when its all across the board like this theres nothing to worry about.
I remember a similar problem a few months back but no analytics info should be lost - theyre just taking their time in updating.