Credit: Jon Kopaloff/FilmMagic

Eddie Cibrian and LeAnn Rimes laughed their way through the orange carpet at Sunday's Academy of Country Music Awards.

But it was hardly a laughing matter when he hit the stage.

When Cibrian, 36, presented an award to Lady Antebellum, people in the press room yelled, "Cheater!"

A year ago, Us Weekly broke the news that Rimes, 27, and Cibrian had an affair while shooting a Lifetime movie. A short time later, they announced that their respective marriages - hers to Dean Sheremet; his to Brandi Glanville - were over.

The new Us Weekly reports that Rimes opened an unofficial Twitter account under the name Wewenlove Feb. 2 and Twittered "Love him!" referring to her one-year anniversary with Cibrian.

Her ex Sheremet Twittered back, "You should feel proud of that ... Considering you were still married [to me] this time last year."

Once he called her out, other people began ripping into her and "she removed that account immediately," a source tells Us Weekly.