The reasons for his un-Robin-like demeanor became surprisingly clear a few days later back home in San Francisco: On March 21 Marsha filed a divorce petition to end their 19-year marriage, citing irreconcilable differences. Friends of Robin, 56, and Marsha, 51, say that their relationship never recovered from the strain caused by Robin's alcohol relapse in 2006 after 20 years of sobriety. While Williams entered rehab and by all accounts has remained sober ever since, "the trust was broken," says a close friend of the couple. "She's hurt." They quietly separated on Dec. 31 (she stayed in their San Francisco home with Cody; he moved to Marin County), but "the marriage," says another pal, "has been over for a long time." Still, the split is "amicable," says Robin's longtime pal Richard Belzer. "It's not a vicious, bitter thing."