Both Star Magazine and The National Enquirer are running stories this week that Jessica Biel and Justin Timberlake are having relationship trouble, so it must be true. Biel and Timberlake, who just went public with their relationship through a series of outings last month, are said to be fighting over Timberlake flirting with other women.

The Enquirer has him flirting with “a young beauty at a turn out the vote event on September 27,” while Star Magazine names the woman he was flirting with that night as actress Kirsten Bell. Both gossip rags have The Hills‘ Lauren Conrad making a unsuccessful move for Justin, with Jessica Biel hearing about the evening afterwards and angrily confronting him.

Supposedly Justin invited Jessica to Toronto to visit him on the set of his film The Love Guru to try and make it up to her after that had that big fight over him flirting with other women:

The trouble began at a Beverly Hills “Declare Yourself 2007” turn-out-the-vote event on Sept. 27, where, an insider says, Justing made a beeline for Heroes cutie Kristen Bell, 27. [Jessica Biel was not there that evening.]

“He was flirting heavily and being touchy-feely with Kristen,” says the insider. “They were talking very closely and holding each others’ arms. They hung out for more than an hour, whispering and laughing with each other.”

At the same time, The Hills star Lauren Conrad, 21, was making a play for Justin’s attention, too. “Everywhere he was, Lauren popped up,” the insider adds. “I don’t think either of these women considered him to be attached to Jessica, based on their behavior. (Though Kristen and Justin were both at the event, a rep for Bell claims they’ve never met.)

When word got back to Jessica, she went ballistic. “Jess just about dumped him on the spot,” says another source. “Justin got angry and said he and Kristen were just friends – but then Jessica ripped into him, demanding to know why all his friends are women and telling him that he needs to focus on her.

“Justin yelled back, saying that’s what he’s been doing. And Jessica told him, not when he’s all over someone else!”

[From Star Magazine, print edition, October 29, 2007]

Star claims that Justin and Jessica patched things up during her visit to see him in Toronto, but that it’s still rough going for them since photos of the two taken on October 9 show then walking apart and looking grumpy. It seems like they could just be annoyed with paparazzi and not with each other, but it could be true that they were fighting, especially if Justin’s flirting was well known.

Jessica is supposedly looking for more of a commitment from Justin. After dating him for ten months, she is said to want him to ask her to move in with him. She is also rumored to be looking for a token of their relationship, like a “friendship ring.”

Justin might have his own reasons to be jealous of Jessica’s friends. While out at a Packer’s game, a female friend of Jessica’s was seen grabbing her butt when Justin had his back turned.

Header image is of Jessica Biel and Justin Timberlake at a Packers/Bears game in Green Bay, Wisconsin on 9/10/07. Thanks to WENN.