Navigation systems relying on GPS could fail today, as well as at the weekend, according to US Air Force and Coast Guard officials. Users are being urged to check their equipment regularly over the next few days. The problem lies with older receivers, which may become confused as the satellite system begins to receive location updates from the ground today. Handsets made after 1994 should be fine, but earlier models could fail or display incorrect information. The Coast Guard says that people should make sure they use more than one method of navigation. Chief petty officer, Rick Hamilton, said that complications arising today could affect people who depend on information from the GPS system for other operations. "We are talking about cellular phone systems, fax and page systems and some power grids," he said. ® Related Stories End-of–the-week bug to eat GPS