Charlie & Denise: The Ring Returns

09/21/2005 at 11:00 AM EDT

Just as Charlie Sheen publicly said that he and his estranged wife Denise Richards are "working toward getting back together," Richards has been spotted sporting a ring on her wedding finger again.

A rep for Richards had no comment about the couple's status, but a source tells PEOPLE that the pair have been spending more time together and with their daughters Sam, 1, and Lola, 4 months.

Sheen, who appeared on The Late Show With David Letterman Sept. 15, said he has two theories about why his marriage hit an iceberg. One: "I was a gigantic ass," he told Letterman. Two: He watched too much sports on TV, neglecting parental duties.

But, he said, the couple are working on their marriage. "I had to take a step back and really take a look at myself and the situation,'' Sheen said. "I made a commitment to this woman that I love, this family that I love and I realized this can be fixed.''

The perhaps somewhat sugarcoated explanation of what went wrong came after more signs that the couple are closer than ever to reconciliation, a happy ending that Sheen said they are hoping to make come true.

"We're working toward getting back together and fixing things," Sheen said. "We have hope. We have a shot."