Hi gbggri1, i'll have a go at answering this for you.
1. NCM to highlight config files not backed up.
I would suggest going into the NCM application and clicking on "Schedule", then select "Create new job". Next, select "Download configs from devices", Next, give the job a name, then choose the date and time / frequency.
Finally, type in your username and password. You will now see this job in your "scheduled jobs" list. I would suggest editing this by double clicking the job, select the "download config" tab and choose the required configs. Next, select the "notifications" tab and fill in relevant info so that an email can be sent out that states which configs have been backed up for which devices. This will help you to discover which config backups are failing and the reason why they are failing.
2. Dates for config files
When NCM shows the running configs were backed up in August, that sounds like you may have scheduled a backup in august possibly? However, i am guessing someone has logged onto the switch since then? If they run any commands, i think they show up as a config change. Has anyone been on the switch via console / telnet etc since August?
Give me a shout if you need any more assistance.
Mike