Computer Does Not Turn Off After Successful Backup

[wedgesture]

Greetings.  My scheduled backups have been running smoothly for several weeks, however the shut down after done function that was selected in the backup scheme has recently stopped working.  This is also happening on my wife's machine.  Then, in the next morning, the computer will shut off while I am working.  I examined the logs, and everything seemed fine.  What can I do?  Thank you for your help.