One thought:
Unless someone has "tinkered" with it, the scheduling details should not have changed but you can review them by going to all programs | accessories | system tools | task scheduler | task scheduler library | Microsoft | windows | backup | in the right hand window right click on Microsoft-Windows-Windowsbackup and choose properties | triggers | highlight daily and select edit
Verify it is set to "recur every day", and "enabled". I would also verify other options under the actions and settings tabs.
