Millennnium bug viruses may have infected computers, where they will lie dormant until 1 January, after which they will wreak havoc when the machine is next switched on.

The warning about "millennium bug viruses" has come from a number of companies that write "anti-virus" software. They say they have detected half a dozen such viruses, transmitted via e-mail, and that more may already have been sent.

The viruses affect computers in a number of ways, ranging from wiping all the data on the user's machine, to having no effect at all because of bugs in the virus's own programming.

The viruses are intended to appear to the unwary user to be a "Y2K" or millennium bug problem, by not showing up until the new year. All share the common trait that, on arrival, they do nothing but check the year date on the machine's battery-powered internal clock.

As long as that is not 2000, they will remain dormant. But as soon as the machine is switched on after 1 January the viruses will go to work and deliver their "payload". Viruses are small chunks of computer code, usually spread as files attached to e-mails. When the file is opened the virus copies itself on to the user's machine.

David Emm, a product manager at Network Associates in Britain, said the most dangerous Y2K virus identified so far was called "Mypics", which would disrupt the internal clock after 1 January.

An unidentified computer glitch left air traffic controllers in the dark today over the whereabouts of scores of aircraft in the skies above New Zealand. Controllers spent more than three hours using a backup system to help guide the planes to their destinations. Authorities were investigating the system failure, but were not immediately blaming problems associated with the Y2K computer bug.

The company which controls New Zealand's air traffic control system, said airports' radars still were operating but were unable to communicate with each other. That meant there was no nationwide picture and controllers could not track aircraft outside of their own range. There were no immediate reports of any serious incidents as a result of the midday glitch, which grounded planes and stranded thousands of passengers across the country.

TAVARES, Fla. - A central Florida trucker is now convinced the Y2K bug can bite and he's staying home until after New Year's Day. Florida officials confirmed Monday they had sent tax notices to John E. Campbell of Tavares, Fla., and about 50 other truckers with a deadline of Feb. 11, 1900.

"It's kind of funny, I guess, but in a way it's not funny," said Campbell, who hauls chemicals to California and brings produce back. He said he doesn't want to be on the road Jan. 1 if things go haywire. "I'll be loaded up, but I'm not going anywhere," he said.

State officials said last week that 97 percent of the state's computers were Y2K proof and would not click over to the year 1900 New Year's Eve instead of 2000. Problems are expected world wide.

Tom Joyce, assistant director of the Division of Motor Vehicles, said division officials caught the tax notice error and are notifying the truckers that the deadline is really Feb. 11, 2000.

"It's a concern. Obviously we don't want it happening," Joyce said. "It was just one little glitch though, and we corrected it."

HORNING'S MILLS, Ontario - Bruce Beach has buried 42 school buses underground near his home in a rural Ontario hamlet in anticipation of the worst disaster mankind has ever seen.

Beach is an experienced bomb-shelter builder and a self-professed doomsayer with an inkling that his moment of truth is finally looming. It may not be January 1, 2000, but it may not be too much later, either.

With help from his son-in-law and three hired handymen the buses have been knitted together in an underground steel labyrinth. He's working on his bunker late into December because the weather is unseasonably warm and time is running out.

The moment he's waited a lifetime for could be just days away.

"Prepare for the worst, hope for the best and expect something in between," is his Y2K motto.

With sleeping rotations, Beach believes he can shelter nearly 500 people. The facility includes air intakes, a nursery, a dentist's chair, a decontamination area and a sound-proof room for people who may have a breakdown.

"If government and big business are concerned enough and making preparations, shutting down pipelines and stockpiling with food...it seems prudent for us to make preparations," said Beach, a 65-year-old with a big white beard who lives with his wife and looks after his 99-year-old mother.

Few Canadians have devoted as much time and effort to safeguard against millennium mishaps as this survivalist, who describes himself as "misunderstood". But then few believe the apocalypse is around the corner.

He built his first bunker in 1964 in Kansas, and would eventually lend a hand in constructing more than 20 of them. Now he has just this one near his house in Horning's Mills, about 100 miles north of Toronto.

He has received e-mails of interest in bunker-making from as far away as Australia and Russia. But he can't find anyone closer to home who shares his interest. "If I knew how to find them I would," he said with a shrug.

He said most people are not interested because they didn't experience the bedlam of the 1960s or the big New York electrical blackout of the same decade.

He believes the millennium bug may not abruptly end the world on January 1 but he says the end could come six months later, following a cascade of geopolitical problems.

"Of course everybody just says 'Beach the nut."'

The Y2K bug found its way into water bills delivered Thursday to about 3,600 customers in West Des Moines. Instead of saying payment is due by Jan. 3, 2000, the bills say there will be an extra charge for payments made after Jan. 3, 1900.

If computers in New Zealand and Australia start to crash at midnight December 31, big corporations in Europe and the United States might still have time to ward off disaster. Tonga and its hundreds of palm-ringed islands in the Pacific will be the first to ring in the year 2000. One hour later New Zealand enters the next century, and two hours later Australia's east coast will be put to the test. Computer experts in Europe and the United States will be monitoring early evidence from the east. Europe has about 12 hours to respond, the United States 24 hours. If you have the same system in Australia as London or New York, you might have time to fix it.