Lindsay Lohan shocked guests at the birth day party of DJ Ruckus at Meatpacking District hot spot SL — by staying sober. “She was totally in control all night,” says a witness. “She basically stayed in one place and hung out with a bunch of girlfriends.” Also at the party were Usher, Nick Cannon and Paul Sevigny. Still, it wasn’t a totally stress-free week for Lohan: On Thursday, a Beverly Hills judge extended her probation for a year after learning that she hadn’t completed the alcohol treatment program stemming from her 2007 drunk driving arrest.