Jennifer Aniston and John Mayer may have called it quits.

That’s the rumor I’m hearing. A source says the pair’s on-again, off-again relationship may have ended sometime within the last week, when Aniston returned from her overseas Marley & Me junket.

“He broke up with her when she got back from her European tour,” the source said.

Aniston’s rep did not immediately comment. Mayer’s rep declined to comment on the singer’s personal life.

But what are their friends saying?

One pal warns that we shouldn’t be quick to assume the two are through for good. As we know, this wouldn’t be the first time they’ve gone their separate ways.

Aniston recently opened up about love and romance to the U.K. magazine You. “Who ever said that every relationship has to last forever? That’s hoping too much,” said Aniston, who turned 40 exactly a month ago. “I think every relationship is a world unto itself.”