John Mayer Ring Shopping for Jen?!

Jennifer Aniston walked the red carpet solo at last night's premiere of "He's Just Not That Into You," but she won't be alone in a few days when she celebrates turning 40!

"I'm going to celebrate with good friends," Jen says of her milestone birthday, "On the beach." The actress is ringing in the big 4-0 with friends -- and possibly an engagement!

The "Marley & Me" star's beau, John Mayer, Twittered yesterday that he visited a diamond store, and was "welding an engagement ring for my girlfriend." Is Mayer joking or serious? Aniston kept mum on her Valentine's Day plans, saying, "That's not up to me," when asked about a romantic way to spend the lovers' holiday.

Jen's co-star Drew Barrymore also dished about her dating life... her love affair with her outfit! "I'm so in love with this dress I might put it next to me in bed tonight and just curl up and say goodnight," the actress joked with "Extra."

Scarlett Johansson showed off a head of freshly dyed reddish locks and was candid when an "Extra" friend asked if she believed women thought about sex as much as men do, Johansson replied, "I'm assuming probably not."

Kevin Connolly was stag at the premiere, telling "Extra" he wasn't suave enough with the ladies to bring a date! "I'm a bachelor," Kevin admitted. "If I had game, I'd possibly have a date to this thing!"