Christina Aguilera has disappointed US fans by reportedly lip-syncing at a gig on Friday night (23MAR07). The BEAUTIFUL star encountered undisclosed technical problems at the concert in Madison Square Garden, New York City, prompting the audience to speculate the star was miming during the entire set. Aguilera's manager Irving Azoff has admitted there was a sound-related problem at the concert. He tells the New York Daily News, "Miss Aguilera is one of the most talented vocalists to ever grace the stage; however, we did have a technical problem with the sound equipment at the Garden."