Can't Perform System Restore from System Tools

I wanted to restore my computer to an earlier time, but can't. I went
through the drill with system performance, files and enabling swystem
restore. After i did all that, I restarted the computer, and tried system
restore. I got a message telling me I had to restart the system first and
then use system restore. I restarted the system, and tried it again---got
the same message about having to restart the machine before I could do system
restore. Then I did a system maintenance. Some bad files were fixed and
some data repaired, then the system went through defrag. I restarted and
tried the system restore after this, and am still getting the same message
about restarting the computer before I can use system restore. What is the
solution? I've tried everything I can think of at this point.