There is Y2K, the computer problem we have lately been hearing a lot about. And then there is Y2K, the people problem that occasionally bubbles to the surface. As it did in Jerusalem early in the New Year when Israeli police arrested 14 members of a Denver-based cult called Concerned Christians, allegedly planning to die in a millennial shoot-out with the police at the end of 1999. They were deported to the United States and disappeared from the Denver airport. The FBI and the Southern Poverty Law Center have been tracking some of the millennialists and survivalist groups that have fixated on the advent of the year with three zeros as a time for the Apocalypse, Armageddon, Doomsday, the end of the world as we know it. What Robert Blitzer, the FBI's counterterrorism chief, worries about is not what the millennialists think, but what some of them may do. He says that many of these groups are "very security conscious, and operate in a clandestine fashion, so we won't know when something is about to happen." The FBI is planning a nationwide assessment of the threat of domestic terrorism on or around Jan. 1, 2000. Mr. Blitzer says, "The odds are that something will happen." The Law Center has analyzed some of the ominous rhetoric these extremists use. Racist preacher James Wickerstrom told followers in Pennsylvania that when the day comes, they should get out of the way for a while and "then go hunting, O Israel." The New American, organ of the far right John Birch Society, warns that the year 2000 may provide an ambitious president with "an opportunity to seize dictatorial powers." Most of the groups gearing up for that day are, at least on the surface, survivalists, concerned with living through the chaos they foresee. Self-styled "patriot" Bo Gritz, in Idaho, hawks pieces of land that he calls "an ark like Noah's Ark." A Preparedness Expo was held last summer in Atlanta, offering "gourmet" dehydrated foods and water purifiers to help survive the terrible day. But along with the survivalist rhetoric, there's a more aggressive subtext. Like the Jubilee, a periodical of the anti-Semitic Christian Identity Organization, saying that when that awful day comes, "internationalism and capitalism will be dealt severe blows." And Anti-Shyster, a magazine published by "patriot" Alfred Adask, calls Y2K a potential "dagger pointed at the heart of Western civilization." If this is what they say in their open literature, imagine what they say in their closed meetings. The FBI's Blitzer says, "There are people who are mentally unstable. You have people who have a grudge against the government for many reasons. The one you don't focus on could be the one to get you." Now these conspiratorial groups have a date to fasten on - New Year 2000. The Law Center has given that date an ironic label, "Y2Chaos." Daniel Schorr is senior news analyst for National Public Radio.