The message you are receiving indicates that there is a lock on your database file. Because of the lock, any additional attempts to access the data file will fail with this message. The lock on the data file is either because you already have Address Manager open, or for some reason there was a problem on your computer which closed the Address Manager program but a process stayed running that kept the lock on the data file.

Check your computer to see if Address Manager is already open, if it is not then usually a reboot of your pc will fix the problem. If it doesn't please let us know so we can help diagnose/fix the issue.