When Robert Pattinson didn't show up to celebrate his 27th birthday at a party Kristen Stewart, 23, had planned on May 13, it was apparent the relationship was in trouble – again. The pair, who met while filming Twilight in 2008, first broke up last year when the actress admitted to cheating with her Snow White and the Huntsman director, Rupert Sanders. But the separation was brief, and the young couple appeared to be back on solid ground. On May 19, however, after the birthday no-show, Pattinson was seen driving away from Stewart's L.A. house in a pickup truck full of his belongings.