Courteney Cox and David Arquette arrives at the St. Joseph Center's 25th Annual Dinner Dance And Auctions Gala on May 1, 2010 in Los Angeles, California. Credit: Michael Underwood/FilmMagic

David Arquette thought long and hard before finally filing for divorce from Courteney Cox on Tuesday, which just happened to be their thirteenth wedding anniversary.

After separating from the Cougar Town actress, 47, in September 2010, Arquette signed documents March 23 of this year, but the Scream 4 actor waited nearly three months to file them.

So why now?

"He's in love with Christina McLarty," one source close to Arquette tells Us Weekly.

He and the pretty Entertainment Tonight reporter first stepped out as a couple in September 2011, split in March, and have recently reconciled. Arquette is hoping to "build a life with Christina," the source says -- inspiring him to finally, officially pull the plug on his marriage to Cox.

Arquette and Cox (who met on the first Scream set and wed in 1999) remained famously amicable during their 20 month separation; their daughter Coco turns 8 on Wednesday.

Although Cox was linked to her Cougar Town costars Josh Hopkins and Brian Van Holt in the wake of her marital split, she complained to Howard Stern: "No guy's asked me out . . . It's time for me to get out there. It's not easy to meet people. They don't call me."