Do you guys think it's more complicated than "her putting was really poor"? I'll admit not to having watched much women's golf or followed all the ups and downs of her career to date. But watching her play this year in Hawaii, at the Nabisco and again this week she putts worlds better than I'd ever seen her putt. Even when she was a kid she didn't putt as well and fearlessly as most child phenoms seem to. But now she has it nailed down pretty darned solid (at least these past few months).
Brent,
I do think that putting is a huge part of her recent resurgence. I'm a believer that poor putting puts stress on the rest of the game. And, conversely, knowing you can make 10 footers more often somehow lowers the stress on the iron game, which lowers the stress on the tee game, etc. 
I think she plays smarter now. Maybe that's what happens when you get a degree from Stanford and get older.
Seriously, I think her course management is much better; she doesn't automatically reach for the driver, plays smart shots into greens, puts herself in positions where getting out of trouble isn't all that problematic. I looked up her stats for the year on the LPGA Tour, and although I view with some skepticism on the use of stats to evaluate players, she's at or near the top of the tour in GIRs -- which, to my way of thinking, means she's managing her game well. She's at a minimum putting herself in position (meaning, on the green) where birdies are possible and bogies are less likely. And her ability to hit a lot of greens means she's putting herself in position off the tee where she's able to reach a lot of greens. That's good course management.
Did she have a really good week of putting? Sure -- anyone who doesn't three-putt at a U.S. Open had a very good week on the greens. But her year-long consistency suggests she's improved that part of her game as well.