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LeAnn Rimes has been separated from her husband of seven years, Dean Sheremet, a source close to the couple tells

"They have been separated for awhile, but are still trying to work on how to handle the problems they are having," the source tells Us. "They are leading separate lives and not staying together most of the time, but still in each others' lives as best friends,"

"They are still not divorcing yet, but are working through things and taking time apart -- as they have been -- while they figure things out," the source continues.

The split announcement comes the same week the new issue of Us Weekly confirms that Rimes is still carrying on an affair with her former Lifetime movie costar, Eddie Cibrian, 36.

Us broke the news of their relationship after spotting the pair on a three-hour tryst at a Malibu Beach Inn last March. Rimes, 26, was also caught on video sucking Cibrian's finger during a dinner date in Laguna Beach, Calif.

Rimes -- who was spotted at Los Angeles' LAX airport Thursday without her wedding band -- married Sheremet, 28, a former backup dancer, in 2002 when she was just 19.

The new issue of Us also confirms Cibrian's wife, Brandi Glanville, left him in light of the fling.

"Eddie and I have decided to take some time apart," says Glanville, 36, mother of Mason, 6, and Jake, 2. "I want to do what is best for our children. Eddie and LeAnn [Rimes] deserve each other."

According to Us Weekly, the final straw came after Cibrian and Rimes were caught again together in the early afternoon of July 17 outside the Malibu home of Jeff Berger, a longtime friend of the singer and Sheremet.

Sources tell Us that Berger has been facilitating similar meetings at his home for about a month and that Rimes and Cibrian also made use of a rental house on L.A.'s west side. (Berger denies he has been enabling an affair. Another source insists Cibrian and Rimes "hung out a bit, but that was it.")


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