incorrect system time (4 seconds off per minute)

Hi all! We have two computers here with the same hardware and software (see below for details), and on one of them the internal timing is incorrect by ~6%, which can be observed in many different ways: * After synchronizing the local clock with an NTP server by the command "net time /set" and waiting for exactly one minute, the local clock has advanced by 64 seconds (after some longer period...