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I'm using VirtualBox version 5.1.6 r110634 on Windows with Fedora 24 4.7.3-200.fc24.x86_64 as guest, both updated to the last patch (both updated two days ago). I have the last version of the Guest Additions installed. And I operate the Guest full screen. The guest, Fedora, GUI freeze on the login, leaving a blank screen (only the background color is visible) forbidding any action with the mouse or keyboard, apparently. To refresh the GUI after a mouse or keyboard typing I have to click on the toolbar of the host, to restore the Windows screen. When I switch back to the guest, the guest screen is updated. After the login screen all comes back to normality.
Received the suggestion to install the latest test build of the VirtualBox Guest Additions fixed the problem.