Late last year, President Clinton praised the Social Security Administration for fixing its basic year 2000 computer problems ahead of schedule. Yesterday, the agency acknowledged sending out letters last month to more than 32,000 people bearing the news that certain benefits would end on Jan. 1, 1900.

Kathleen Adams, assistant deputy commissioner for systems at the Social Security Administration, attributed the 100-year date error to a glitch in the program that printed the letters. "Mission-critical" computers that generate checks are fully compliant, she said, but there may still be a few bugs to work out in less important systems.

"We're confident that all of the programs that determine who is eligible for benefits, and for how much . . . are ready," Adams said. "There was no error in identifying who was to get these notices, and each was sent to the proper address," she said.

The notices, sent Aug. 22, went to families with dependents receiving Social Security benefits under the administration's survivor program, designed to financially aid families whose breadwinner has died or become disabled. Payments can be stopped after the dependents turn 18.

New notices with the corrected date were sent Wednesday.

The year 2000 computer problem--Y2K for short--stems from the use of two-digit date fields in many computer programs and chips, which can cause the machines to interpret "00" as the year 1900, instead of 2000. Such a reading can cause a system to relay faulty data, malfunction or shut down completely.

The Social Security Administration issues checks to about 48 million Americans each month. As the administration's computer programs rely heavily on dates to calculate age and benefits, few other federal agencies are as potentially vulnerable to Y2K problems.

For this reason, Adams said, Social Security began working on the problem in 1989, and has spent close to $40 million sifting through 35 million lines of computer programming code. So far, it has changed about 3 million lines to bring systems up to date.

Adams said the "cosmetic" display programs--those that contain dates not used for age computations--have not been as rigorously tested as those that determine eligibility.

"What we're doing now is taking another look at these display programs and looping them back again and again to make sure we don't have another embarrassing situation like this," Adams said.