Record locked by another user

[Allie]

I have a form and a sub form - the sub form is a datasheet.

Each time the form opens it prompts the user to enter
their ID and only displays data for that ID. However,
when users try to enter data into the sub form, they
receive a message saying that the record is locked by a
paritcular user.

I have the database set to
Default Record locks - no locks
Default open mode - shared

Any suggestions?

Thanks