The fickle flame of love has fizzled -- yet again -- for a pair of inconstant celebrity couples. According to reports, not only have Jessica Simpson and John Mayer parted ways for the second time in less than a month, but Kate Hudson and Owen Wilson are also finished after almost a year of fitful togetherness.

Let's start with Jessica, 26, and John, 29, who apparently went belly-up just days after jetting to Cabo San Lucas, Mexico, for Memorial Day weekend, a getaway that turned out to be as relaxing as a sand-filled bikini bottom.

According to Us Weekly, the indecisive squeezes, who called off their romance in mid-May only to reconcile days later, spent their seaside sojourn squabbling.

"Jessica and John were horribly fighting in Mexico," a mole tattles to the mag. "They were supposed to go out to dinner one night but stayed in because they were fighting and didn't want to be seen in public. ... They didn't even sleep in the same bed for at least the last night!"

Paparazzi caught the dimpled duo purportedly engaged in a tearful spat outside their villa on May 26, with the lately shorn and hotter-looking crooner, cradling Jessica's dog Daisy, eventually stalking off, leaving the stacked starlet with her head in her hands.

"She seemed really sad," says an eyewitness.

Us claims they ended up heading home a day early, with things coming to their inevitable conclusion during a final telephone tiff on June 3.

So what did them in this time?

One insider brushes off speculation that Mayer pulled the plug because he's afraid to settle down, instead pointing the finger at their contrasting personalities (e.g., he likes to read, she likes to expose her cleavage).

"He does not have commitment issues," the snitch insists to Us. "They are just very different people and the differences came through."

A Mayer source pipes in to People that the relationship "has been rocky and it had been rocky, and it reached the end of the road," adding for good measure, "It is definitely over -- the relationship has ended."

Still, a Simpson confidante remains optimistic about Jessica and John's yo-yoing affections, telling the mag, "They broke up Sunday night, but who knows what the future will hold. This is the twelfth time they've broken up. Their relationship is volatile. Last week they felt better than ever. This week, things are rocky. Who knows what the future will bring."

(Let us channel the Amazing Kreskin for a moment and save everyone some time: The future will hold ... breakup No. 13.)

For now, Mayer is back on tour and Jessica is back on the town. She hit a Los Angeles hot spot Tuesday night with her girlfriends, with an eyewitness enthusing to People, "She was super happy and upbeat."

Meanwhile, did commitment issues spell doom for Kate and Owen?

That's the word from the New York Post, which says the willowy actress, 28, was recently overheard at an NYC soiree kvetching about how weary she was of waiting for the Butterscotch Stallion, 38, to stop running wild.

"She said that if he didn't step up and make time for her, then she was over it," a spy tells the paper. "A few days after that, she broke up with him over the phone."

Adds another source, "They've broken up and gotten back together a million times. She's complaining to everyone that she made all these sacrifices and he can't be in a committed relationship."

The look-alike lovebirds reportedly hooked up in August 2006, shortly after Hudson's marriage to rocker Chris Robinson crashed and burned (they have a 3-year-old son, Ryder). They were rumored to have parted ways late last year, only to reunite a short time later.

Reports that Kate and Owen are kaput come soon after they ended their long-running game of duck-and-cover with the paparazzi by cuddling at an NBA game, smiling as they left a see-and-be-seen Los Angeles eatery, and stepping out for the premiere of Wilson's flick, "The Wendell Baker Story."

"They're still friends," an insider assures People, which says the breakup happened just before Memorial Day weekend. And besides, they'll always have their craptacular comedy, "You, Me and Dupree."

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