Report: Jennifer Aniston and John Mayer Split

Jennifer Aniston and John Mayer may have split – again – according to E! News.

A source tells E! that the famously on-again, off-again pair may have called it quits sometime within the last week, when Aniston, 40, returned from her European junket for Marley and Me.

PHOTOS: Click here to see photos of Jennifer Aniston.

“He broke up with her when she got back from her European tour,” the source told E! spotted Mayer drinking alone out in Calabasas on Monday at the Crown and Anchor Bar and Sunset Terrace Bar. While Mayer mingled with the locals, Aniston was nowhere to be found.

A rep for Aniston declined to comment on the matter Thursday, telling, “We don’t comment on … rumors about her personal life.”

PHOTOS: Click here to see Jen's famous romances.

A rep for Mayer was not immediately available for comment.

Still, while friends of Aniston warn that people shouldn’t assume the two have called it quits forever, the star recently offered a somewhat pessimistic take on love to U.K. magazine You.

"Who ever said that every relationship has to last forever," she asked. "That's hoping too much. I think every relationship is a world unto itself."

Aniston and Mayer went public with their relationship for the first time last month when they attended the Oscars and the Vanity Fair postshow party together.

LINK: Click here for the E! report.