Jennifer Aniston Unhappy at John Mayer's Cheating Joke

Jennifer Aniston "wasn't happy" when he beau John Mayer told the audience at one of his gigs that he'd had a dream in which he was "making out" with someone other than his girlfriend.

A source close to the pair -- who have been dating for nearly three months -- said the former 'Friends' actress was left furious by John's remarks.

"One of the things that causes tensions between them at times is the jokes John makes wen Jen isn't around," the source tells Britain's Now magazine. "She wasn't happy when he told the audience at his show in California on July 26 that he had a dream he had 'made out' with someone other than her."

John, 30, then dedicated 'Dreaming With a Broken' Heart to Jen, saying he had to make it up to her by singing that song.

"John has a quirky sense of humor, which is one of the things that attracted Jen to him in the first place, but she didn't see the funny side of that," said the source.

"He's always putting updates on his blog about his personal life. Just recently he joked on it that he'd been arrested, but really he was talking about playing Grand Theft Auto.

"John's also happy to speak to the paparazzi when they film him for gossip blogs. It isn't really Jen's style, but she's learning to accept he's more laid back than she is about a lot of things and he can laugh his way out of difficult questions

"It shows how much she likes him that she's prepared to put up with that."