The Pentagon said a U.S. military spying system was blinded for about three hours because of a Y2K failure. A back-up system partially restored operations while software patches were being made.
An Amtrak computer that tracks trains failed temporarily in Saturday's early hours, but operators quickly switched to a manual system and fixed the software.
Computers at five nuclear plants across the country also reported some temporary problems, but none was related to plant operations or safety.
The U.S. Naval Observatory, which has a master clock in Washington keeping the nation's official time, reported Saturday's date as Jan. 1, 19100, on its Internet site. The glitch, which was corrected, affected only the Web site, not the master clock.
Some 150 slot machines at three Delaware race tracks failed briefly because of a Y2K bug.