Kim Kardashian Celebrates Her 31st Birthday With Hubby Kris Humphries

Amid reports Kim Kardashian and Kris Humphrie's new marriage is already on the rocks, Kim proved the rumors false last night, showing the world there's a different kind of "rocks" in her marriage -- in the form of a huge, heart-shaped pave diamond necklace!

Nevermind the humongous engagement and wedding bands that almost prohibit Kim's left ring finger from bending ... girlfriend's got this huge weight around her neck and, we hope, a hefty insurance policy to go with it! Still, it wasn't a gift from Kris -- Kim's been seen sporting the jewel for a while. Wonder what Kris got for her?

The newlyweds celebrated Kim's birthday at New York hotspot The Darby Friday night, along with Kim's sisters Khloe and Kourtney and Kourtney's beau Scott Disick.

A highlight of the night was when Kim's BFF La La Anthony sang a Stevie Wonder version of "Happy Birthday." Then Pink sang The Fugees' "Killing Me Softly" as Kim and Kris danced.

But as one party wraps, another one is set to begin. Kim's off to Vegas to celebrate again tonight at Sin City's Marquee nightclub. She'll also be celebrating a new job -- the reality show star will take on her second big-screen role in Tyler Perry's upcoming The Marriage Counselor. Maybe that's something she knows about?

Kim will play a marriage counselor's assistant, Ava, who helps her friend gain confidence with a makeover and other boosters. The story's based on Perry's play by the same name. It starts filming next week in Atlanta. Busy, busy, busy!

She Tweeted a photo of her luxurious ride outta the Big Apple ...