Now that Dan Abrams has given up his MSNBC show to run the third-place cable news outlet, he might want to focus on the rising tensions between two of his prime-time personalities: Keith Olbermann and Rita Cosby. Olbermann, whose "Countdown With Keith Olbermann" airs weeknights at 8, apparently has precious little respect for Cosby, whose "Rita Cosby: Live & Direct" airs at 10 p.m. "Rita's nice," Olbermann wrote to a fan from his MSNBC E-mail account, "but dumber than a suitcase of rocks." Yesterday Cosby retorted: "Keith got it wrong. I'm not that nice." But a Cosby intimate gasped when...