HBO’s airing of Michael Jackson’s concert in Bucharest, Romania, on Saturday night was the pay cable net’s highest-rated special ever, scoring a 21.4 rating, 34 share in HBO’s 17.5 million homes.That means approximately 3.7 million homes tuned in to the 90-minute special, which was part of the pop singer’s “Dangerous” tour. The Oct. 10 telecast was the first time Jackson has allowed one of his concerts to be aired on TV. While the performance was a high for HBO, it translates into about a 4 rating for the traditional TV networks. Network viewing levels were somewhat lower Saturday in the overnight markets, which may be attributable in part to the Jackson special. Aggregate network viewing was boosted by tune-in for the baseball playoffs. The performance put the Jackson concert on par with the airing of one of Madonna’s “Blonde Ambition” tour concerts on HBO. That special scored a 21.5/31.