When I select scan the screen reverts to the scan security main menu If I reboot it works why do I have to reboot?

When I go to the security main menu and select security and then scan (any scan) when i hit return the screen returns to the main security screen. Scans will not run. All other functions (performance, etc.) seem to work ok. When I reboot scans then work but next time same thing. Is this a bug in my program? thanks.