Air America's difficult birth, caught on film HBO's documentary on the liberal-leaning radio network chronicles its tumultuous first weeks.Air America Radio, the left-wing talk-radio venture featuring Al Franken, Randi Rhodes and Janeane Garofalo, celebrates its first anniversary on the air this week, and HBO is giving it a rather macabre gift to mark the occasion: a searing, warts-and-all documentary showing just how perilously close the fledgling network came to oblivion in its first weeks. "Left of the Dial," which premieres on HBO on Thursday (8 p.m.), was supposed to be a relatively benign insider's account of the launch of Air...