RentMaster has recently released version 9.1.  One of the changes in this version is important for anyone who is running Windows Vista, and who is not running RentMaster as an administrator.  If you are running windows Vista, but are not sure if you are running RentMaster as an administrator or not, then you should probably assume you are not.  If you are not using windows Vista, you wont have any problems.

If you are one of those people affected, your database backup may not be backing up the correct database file, as windows Vista may have created a second database file without your knowledge, and you are still backing up the original database file which does not have your current data in it.

More information can be found here.

http://www.rentmaster.co.nz/blog/2009/10/Coming-in-v91---Backup-issues-for-Vista-users.aspx

Updating to the latest version is recommended.  To update, go to the Help menu and choose Download RentMaster Update.