After a reboot, I cannot configure my normal VPN connection, nor modify some Operating System security settings.
What can prevent me from making changes to security settings? Malware?
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Applications which interfere with screen appearance can prevent a user from makes changes to security settings while the app is active.
The operating system has to be careful to prevent a 3rd-party application from having influence over security settings by changing the appearance of security options to the user. (best guess speculation)
A screen-color-changing app, Twilight, may have been active, and therefore, from a Security Manager's point of view, able to influence a user's input to system security settings menus.