Do you have a dual-boot system with Windows XP? Windows XP does not understand multiple restore points and it silently deletes them whenever it mounts a volume that contains them.
Thanks for responding. No, I don't think I do. Although I have Windows 7 Ultimate, I haven't used the XP format. But...maybe I have and did not know it. I would have thought that I would have been aware of this "dual-boot system", of which I have not been made aware. I do understand that XP is a part of Win 7 Ultimate. I just did not know how XP would manifest itself. I was not aware that it was active. thx Jim
If you were dual-booting XP I'm pretty sure you would know about it - it's not the same as running XP inside a virtual machine as part of Windows 7.
Do you have restore points enabled? Click Start -> right-click "Computer" and select "Properties". Then click "System Protection" in the left pane and look at what's shown for the disk drives under "Protection Settings". It should say "On" in the protection column.
If protection is turned off then that's the problem. If not, then click on the drive to highlight it and click the "Configure..." button and check the maximum space slider to see how much space you've allowed for system protection. If you've allowed very little space then that might be the problem.