Never allow two users to open the same database at the same time.
You need to split the database into a frontend (contains forms, queries,
reports, etc.) and a backend (contains just the tables, to which the
frontend links). This can be done via Tools | Database Utilities | Split
Database option.
Then each user has his/her own copy of the frontend, and both can then use
them simultaneously.

Signature
Ken Snell
<MS ACCESS MVP>
> I am having problems when two people are trying to access
> the database at the same time. Only first person who
[quoted text clipped - 3 lines]
> command no longer valid. Can anyone help me fix this
> problem.