David Letterman's show has been knocked off the air in seven southern and midwestern cities -- including Wichita, Mobile and Mason City -- this week because the stations' owner, Nick Evans (of Spartan Communications in Spartanburg, S.C.), had trouble getting tickets for people who wanted to see the "Late Show" taped in New York. Instead, viewers of Evans' stations are being treated to a mixture of infomercials, sitcoms such as "Mama's Family" and "Married With Children," and "Judge Judy." Evans concedes that a ticket dispute was behind his decision, but also says he's unhappy with Dave's low ratings. "I don't think it harms viewers," Evans said of his scheduling switch. Said Rob Burnett, executive producer of the "Late Show": "I think this is the type of fellow who is used to getting the best table at a restaurant at a moment's notice while the rest of us have to wait in line."