Amid allegations that he had a fling with a stripper, Josh Duhamel and Fergie appeared as a united front during a dinner date in Atlanta Tuesday night.

Fergie, 34, and Duhamel, 37 – who's in town filming Life As We Know It – dined at Chops restaurant, which is located next door to the St. Regis Hotel, where exotic dancer Nicole Forrester claims she had a one-night stand with Duhamel Oct. 9.

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At dinner, Fergie and Duhamel didn't seem the least bit troubled.

Sitting close together in a rounded booth in the center of the restaurant, they shared a bottle of Chardonnay and dined on steak and lobster upon arriving around 10 p.m.

As they left (Duhamel paid for their meal), they even greeted some fans and took photos in the restaurant, a source tells "She swung by the kitchen because it's an open kitchen and said, 'Great dinner,'" the source tells Us. "She was complimenting the chef. She was very friendly and genuine. They seemed really happy together."

A source tells the new issue of Us Weekly (on newsstands now) that Fergie "says nothing is wrong" with their marriage, despite the infidelity claims.

Says another, "Josh told her it didn't happen, and she believes him."

Yet a lawyer for Forrester, the stripper, says the dancer has passed a lie-detector test and is in possession of racy texts from the Transformers star that corroborate the affair.

Attorney Romin Alavi also tells Us that Forrester -- a 34-year-old mother of two -- didn't seek out the the National Enquirer (which offered her $20,000 for the story) in hopes of a payday.

"Josh bragged about what happened on the set of his movie [Life As We Know It], and someone called the Enquirer with the tip,” Alavi tells Us. "The Enquirer then came to Nicole."

For more on Duhamel's alleged fling - including how he is "annoyed" at how she parties "too hard," how their long-distance work has caused "strain" in their 10-month marriage and whether friends think they'll weather this latest stripper scandal - pick up the new issue of Us Weekly today!