It sounds like you have a Task set up to Backup up your system and this message is related to it.
As far as the operations log, you might check the Event Viewer to see if anything mentions the message there. (Eventvwr.msc)
Look in the Summary of Administrative Events to see what errors or warnings, or perhaps even notifications. You can expand them to see the individual entries and double click them to get specifics.
If you have some type of third party backup software, it will probably have its own log.