12AM sounds like you're looking at a field that has been formatted
(perhaps incorrectly) as "Time", and the time is 0, whereas you meant
"General Date" or some other format including the date..

Shifting values: sounds like a logic problem in the source code.
Access (better: Jet) doesn't just shift values around. Heck, they may
not even fit because the next field may be an incompatible data type.

-Tom.

A few things:

when access 2000 came out it had a tremendous amount of bugs, and problems.
This means you must apply all the service packs and the updates to both
office (access), and also install the updates to the jet database engine.

The next thing you need to ensure is are you talking about a multi user
environments, and if yes, then you must split your database, and preferably
distribute a mde to each WorkStation. While access 97 would "tolerate" a
setup in which more than one user was in the front end at the same time, it
generally was a bad idea. Later versions of access are far more sensitive to
this issue, and will suffer from frequent corruption and damage to the code
system if you don't install a copy on each WorkStation. (assuming we're
talking about a multi user environment here).

I explain the concept of splitting here:
http://www.members.shaw.ca/AlbertKallal/Articles/split/index.htm

So in addition to splitting, try distributing a mde to each WorkStation.