Kristin Cavallari Photo by: WESTLEY HARGRAVE / SPLASH NEWS
Don't Look Back| Nick Lachey, Individual Class

What's Up with Kristin?

Exactly what constitutes a hookup is a matter of great national debate, but this much is certain: Lachey is back on the market. Recently he's been spotted out in L.A. on a few occasions with Kristin Cavallari, 19, best known as the boy-killing mean girl on the MTV reality show Laguna Beach.

But the hookup – however it's defined – is "not anything serious," says a friend of Lachey's. And then there's Cavallari's recent hookup with her ex-boyfriend Brody Jenner, 22 (son of Olympian Bruce), at a March 17 fashion show in L.A. "She isn't with Nick," a friend says of Cavallari, who also briefly dated Lachey's pal, USC quarterback Matt Leinart. "She was with Brody at the 2BFree show and then at the [nightclub] Lobby. They made out and left together."

• By Michelle Tauber. K.C. Baker and Tiffany McGee in New York City, Marisa Laudadio, Kimberly Lansing, Shannon Bradley and Vanessa Diaz in Los Angeles and Lesley Messer and Angela T. Koenig in Cincinnati
This week's cover

On Newsstands Now!

JOSH & FERGIE: ROCKED BY SCANDAL

Did he cheat with a stripper?

Married less than a year, the couple denies an Atlanta woman’s claims that she and Josh had a fling
Note that this week’s cover of PEOPLE may differ regionally

Save $1.00 off this week's issue. Click here for coupon