Credit: ROBYN BECK/AFP/Getty Images; Dimitrios Kambouris/Getty Images for Dior

That was quick.

A source tells the new issue of Us Weekly (out now) that newly divorced Ryan Reynolds, 34, ended his brief summer fling with Charlize Theron, 36, in late July. "He only wanted something casual, but she's in a rush to settle down, have kids and start a family since she's getting older."

The source adds that the Prometheus actress "didn't take it very well when he broke it off. She knows deep down that it wouldn't have worked, but she is pretty bummed out about it all."

No wonder. Things seemed so promising for the private pair, who managed to stay off the radar until Reynolds was spotted emerging from the Oscar winner's Malibu home June 5.

Set up by mutual pals, the former neighbors (who had known each other for several years) realized they had a spark from the beginning. But Theron's family focus, compounded with conflicting schedules, forced Reynolds to end it. "They're both too busy," a Theron pal tells Us of the long-distance couple. "And they were hardly ever together anyway."