Are you talking about records or are you talking about users getting locked out from the database and tables?
If records, check the settings and ensure what has been set against the database is 'Edited Records'. It is also possible that a setting in the registry is not set high enough. I know in 97, 2000 the Max Record Locks was set to 9600 by default. I do not know the value for 2002/03. However, this should be set at least to 100,000.
We switched from Access 2000 to Access 2003 and have since discovered a problem where a lock occurs on large tables that did not occur on 2000...
Anyone?