Hope springs eternal for Charlie Sheen. A little more than a year ago, he was in the middle of a knockdown, drag-out divorce with Denise Richards, who accused him of, among other things, threatening to kill her. Now, the "Two and a Half Men" star is once again ready to commit himself to the institution of marriage.

Us Weekly says Sheen, 41, has asked real estate investor and fellow optimist Brooke Mueller, 29, his girlfriend of approximately a year, to be his third wife, popping the question during a weeklong getaway to Costa Rica. (Sheen's spokesman, Stan Rosenfield, confirmed the news to the Associated Press on Thursday.)

The actor reportedly closed the deal by hoisting a $500,000 sparkler onto Mueller's apparently buckling finger (with his $350,000-per-episode paycheck, he can easily afford the retina-scorching ring).

"The two bring out the best in each other," his buddy tells the mag. "Brooke is a good influence on him."

Sheen, who has two daughters with Richards -- Sam, 3, and Lola, 2 -- hasn't always had the best track record when it comes to romance, unless you count the 5,000 women he's purportedly bedded (that's according to Maxim).

His engagement to Kelly Preston (now Mrs. John Travolta) went belly-up in 1990 (likely contributing to their demise: The wound she suffered when one of his guns accidentally fired), and his 1995 marriage to Donna Peele barely lasted a year.

As for the second Mrs. Sheen, she appears to be doing her best to play nice. Not only was Richards recently photographed out and about with Mueller but she's also very publicly extending her best wishes to the pair.

"I am genuinely happy for the two of them," Denise helpfully informs People. "In fact, I sent them flowers to congratulate them both. I've spent time with her, and my girls really like her. That's all that matters to me."

Still, she may have emitted a deep sigh over Sheen's tropical proposal in light of whispers over how her ex, Richie Sambora, ended their not-quite-yearlong affair.

According to the New York Daily News, Denise thought the Bon Jovi guitarist and ex-hubby of her former BFF Heather Locklear was planning to pop the question during their Hawaiian vacation earlier this year. Instead, he allegedly gave her the heave-ho.

"She was devastated," an insider tells the paper, "and kept up appearances as if they were still together."

Richards, however, says the engagement story is so much hooey.

"That is 100 percent completely false," she insists to People. "There were a lot of rumors about our relationship from day one and we broke up for many reasons. Richie is a great guy and an amazing father. I really wish him well."

Denise, by the by, also deserves some props for self-awareness. When "Extra" recently asked if she had any words of wisdom for parolee Paris Hilton, she said, "I am truly not one to give advice. I'm divorced and I stole my best friend's husband."

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