J-Lo 'n Ben... Spliting up?

Ben Affleck and Jennifer Lopez, who just days ago were planning their weekend wedding, have split up, sources close to the couple tell PEOPLE.
The break-up comes in the wake of their decision Wednesday to postpone their Sunday wedding in Montecito, Calif., before as many as 400 guests. The couple blamed the delay on excessive media attention surrounding the event, but reports persisted that Affleck was having second thoughts about the nuptials. A PEOPLE source says it was Affleck who initiated the split.

While it was unclear whether the separation was permanent, Lopez was "devastated," according to one friend. The star was in tears, sources said, on Wednesday as she called guests telling them of the wedding's postponement.

Lopez, accompanied by friends and a bodyguard, went for a very public jog and swim -- at one point changing into a bathing suit behind a phalanx of towel-bearing guards -- Saturday afternoon along Miami's South Beach, not far from her 11-bedroom house in Miami Beach, where she flew solo on Friday from Los Angeles. Affleck was believed to still be in Los Angeles, though some reports had him heading to Las Vegas for tonight's Shane Mosely-Oscar De La Hoya fight.

The split caps a tumultuous summer for the couple, whose romance became public in July 2002 just days after she divorced Cris Judd. They have endured brutal reviews for their performances in the film "Gigli," while tabloid reports have accused Affleck of misbehaving with strippers during a late-night visit to a Vancouver nightclub (reports he vehemently denied). Lopez publicly stuck by her fiancee ("for me, it wasn't an issue," she told W magazine), and plans continued apace for their wedding -- his first, her third.

Ken Sunshine, Affleck's spokesman, said he had no knowledge of a split. Lopez' spokesman Dan Klores said he believed the couple was still together, but had not spoken to Lopez in several days.

During their time together, the pair -- who met on the set of "Gigli" -- generated worldwide attention, costarring in a sexy music video for her song "Jenny from the Block" and purchasing each other extravagant gifts, including a Rolls-Royce, a Harry Winston bracelet of white and yellow diamonds and 6.1 carat pink diamond solitaire Affleck gave Lopez as an engagement ring. Nevertheless, they thought of themselves as working-class kids -- she from the Bronx, he from Boston -- who shared similar values. As a teetotaler, Lopez was also seen as healthy for Affleck, who is a recovering alcoholic.

The couple will be together again -- at least on screen. Their second costarring vehicle, "Jersey Girl," is set for release next year.