Season 7 of 24 promises to be its tensest yet — at least on the set. Execs at the Fox hit have scrapped virtually their entire story line for the season, delaying the start of production by roughly three weeks. According to sources, the 11th-hour time-out was called after the network put the kibosh on a costly plan to shoot a number of episodes in Africa. Producers briefly toyed with the idea of finding a location in Los Angeles that could sub for the continent, but they ultimately decided to ditch the whole concept and start over from scratch. Although...