According to those who observed them on a holiday vacation to Puerto Rico, nothing.
The couple, who left for their romantic jaunt on Dec. 26, rang in 2009 poolside at La Concha Hotel, reports the Puerto Rico newspaper El Vocero.
On their trip, which lasted through the first week in January, the couple also attended the gubernatorial inauguration and had a cozy dinner together at Marmalade restaurant in Old San Juan.
What's more, a reliable source tells PEOPLE that Lopez, 39, and Anthony, 40, are seriously considering purchasing property at Trump's International Gulf Club Puerto Rico, where they took a tour over the holiday.
'They've Been Arguing'While both their reps tell PEOPLE that the couple are "great," insiders indicate that their marriage isn't perfect. "They have been having problems, like in any marriage," says one. "They've been arguing."
The likely cause? The growing pains naturally associated with raising 10-month-old twins Max and Emme.
"The marriage is experiencing frustrations because of the added stress of the twins," says another source familiar with the situation, "but they will work things out. They love each other, and that will dictate what happens. I don't think divorce is in the picture."
With reporting by K.C. BAKER, VANESSA DIAZ and LINDA MARX
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