Unable to Export / Import in Access 2003

Since updating our database to Access 2003, I have not been able to export /
import reports queries or anything between different machines.

We use an access "Front End" and a SQL back end. I have several users in
customer service and when I create or change something in one interface, I
have to go to several other machines to make them all current. Before I
could export from one machine to another.

I get a message telling me it can not create a lock.. Can anyone explain
how to fix this???

Thanx
Tom