Five days after the transition to all-digital television, WUSA, the area's CBS affiliate (Channel 9), and WJLA, the ABC affiliate (Channel 7), have disappeared from screens around the region. The stations were the only two in the Washington area to move their digital signals from UHF to the VHF frequencies they once used for their analog broadcasts... LaRochelle received the stations perfectly before the digital transition on Friday, when all full-power stations permanently turned off their analog signals. But now, "they don't even register after a rescan," he said, although he is able to receive Baltimore's ABC channel... The sudden...