Just weeks after checking into rehab for alcohol, Amy Winehouse proved the brief stint did nothing to help her clean up her act. Winehouse made a major ass of herself at a concert in Serbia over the weekend, which was branded "the worst (concert) in the history of Belgrade." Winehouse put on quite the performance for concertgoers. Among the 27-year-old's antics on the opening night of her concert tour were forgetting the lyrics to many of her songs, walking around in a drunken stupor and leaving the stage over and over again during the 90-minute show, part of which was carried by her back-up singers. The crowd of 20,000, who paid a whopping $57 per ticket, responded with boos and catcalls. Winehouse didn't make any fans when she bid the fuming crowd a greeting of "Hello, Athens," which would have been fine if she was in Greece, not Belgrade, Serbia. It was enough of a hot mess to cause Winehouse to cancel her remaining shows. Wino's spokesperson issued the following statement following the embarrassing debacle, "Despite feeling sure that she wanted to fulfill these commitments, she has agreed with management that she cannot perform to the best of her ability and will return home. She would like to apologize to fans expecting to see her at the shows but feels that this is the right thing to do." The European summer tour was supposed to be her comeback and included stops in Turkey and Greece. Winehouse has supposedly been working on a follow-up to her 2006 album Back to Black, but nothing has materialized yet ... and it likely never will if she stays in this shape.