For a few hours at least, things seemed back to normal for Charlie Sheen and Denise Richards. On March 12, 10 days after Richards filed for divorce from Sheen, the pair gathered with about 50 friends and relatives (including Sheen's dad, Martin) at their Agoura Hills, Calif., home to celebrate their daughter Sam's first birthday. Sheen and Richards, seven months pregnant with their second child, were cordial to each other at the party, which they had begun planning more than a month ago. Says a source: "They want to be good together in front of their daughter."

But now it seems certain the party is over for good for Richards, 34, and Sheen, 39, who married in 2002. Initially, sources said, Richards filed for divorce as a wake-up call to Sheen, who, she believes, had rediscovered some of his old bad habits. Sheen denied any relapse, and now Richards "is going through with the divorce," says a source close to her. "There is no getting back together."

That still leaves the question of what drove them apart. Sheen, who completed rehab for alcohol and drug abuse in 1998, has denied any bad behavior or infidelity. Two sources close to Richards say her concern about Sheen's alleged gambling played a part in the rift. Don't bet on it, says Sheen's rep Stan Rosenfield: "He does not have a gambling problem." Rosenfield calls such claims "innuendo, and he's an easier target because of his past." Instead, says a Sheen pal, the couple had simply grown apart. "They like to do different things," says the friend. "Charlie is more of a stay-at-home guy, and she likes to go out more and be more social."

As the pair adjust to the split, they have focused on work: Sheen resumed production on his CBS sitcom Two and a Half Men after a scheduled weeklong hiatus, and Richards continued filming the UPN drama pilot Wildlife and the movie comedy Edmond. She also shopped for maternity wear at A Pea in the Pod with her mother, Joni, and attended a belated 34th-birthday dinner March 11 with a few female friends, including Sheen's Spin City costar Heather Locklear. Says a source: "She's moving on."

So is Sheen, who loaded his belongings into a moving van March 7 and headed for a nearby apartment, where he can be close to Sam. "He's taking the high road," says Rosenfield, "and we're keeping it private."

By Jason Lynch. Elizabeth Leonard in L.A.