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John Mayer and Jennifer Aniston: Back on?

Nope. A new cover story in OK! magazine claims that former flames Mayer, 32, and Aniston, 41, have gotten back together. A rep for Mayer tells exclusively of the OK! story and other reports: "John is single. These reunion rumors are 100-percent fabricated."

A source adds of the singer: "After his tour wrapped on September 11, he traveled back to his NYC home. He's been out with friends and catching up on much-needed rest."

Just last month, Mayer publicly addressed similar rumors about an Aniston reunion. "I'm completely single!" he told the crowd at an Aug. 24 concert in Irvine, Calif.

Another insider recently explained of the former couple: "John is still friends with Jen, but they are not dating again...They remain friends but are definitely not back together."