This error could mean a variety of things. 

• If the file is not in use, then the file is likely locked open.  If you are using a stand alone PC, reboot it.  If you are using a network, make sure that another user doesn't have this file open at his/her workstation.  If it is not open at any workstation, reboot the server.

If neither of the above, resolve the situation, please contact AMS technical Support via email support@1099-Etc.com or phone, 405-340-0697.