Access 2000 error: Could not update currently locked

We have a nice Access 2000 database, residing on a nice fast server, used by
six users on Windows 2000 and Windows XP workstations. About twice a day we
get the error "Could not update currently locked", and the only fix is for
everyone to exit from the database; then we can restart it and it works OK.

The users haven't been able to spot any trends or offer any clues about when
or why it happens.

Can anyone offer any suggestions about what might be causing this, or how I
can go about troubleshooting it? Thanks!