I have an existing Microsoft Access 2000 database that is split with front end/back end. It is on a network file server and is accessed via network shares. There is a current group of users who have been successfully accessing it simultaneously; some using Windows 2000 Pro/Office 2000 and some using Windows XP Pro/Office 2003. I am now adding 2 new users, 1 2000 Pro/Offc 2000 + 1 XP Pro/Offc 2003, who each get the 'cannot lock file' message if anyone of the original group is using the database, otherwise they can access the file. Further if either of the 2 new users log on first, any of the original users can use the database but only as read-only. Both original and new users all have the same NTFS permissions to the database and folders on the network. Any help to solve this will be most appreciated.
No they don't.
Absolutely 99.9% guaranteed.
The only other possibility is that the new users have their default database open mode set to exclusive. Since this is not the installation default it is very unlikely to be so.
(Tools>Options Advanced tab)