BackUp Warning Constant! How do I stop the warning?

BackUp Warning is constantly telling me to BackUp, even when I had a complete BackUp within minutes!  I tried setting several different schedules for BackUp with no change in the warning message.  I do my BackUps to an external "F:" hard drive.  Norton 360 already asked me to re-format the disk and perform a complete BackUp, continuous warning message despite re-format and BackUp today.  I also spent a couple hours today creating a mirror image of all of my document and photograph files to my laptop computer from my desktop computer, so that all of my important data is saved independently of Norton 360 BackUp.  I also have done BackUps using Acronis as well as Norton to another hard drive indicated as "D:" hard drive.