In Exchange 2003 scheduling is handled by the Schedule+ free/busy system folder in your public folder database. If you have more than one exchange server make sure this folder is replicating and synchronizing between all the servers. You can use PFDVAdmin to view and make changes to the replication status. Install this tool on your pc, not the exchange server. You will need both dotnet 1.1 and 2.0 installed on your system. I would also modify the replication schedule to “always run” if you want the calendars to update the free/busy times for all users as soon as changes are made.