Unable to login on windows host after Lock

[harufu]

Here is my situation:
Windows 7 Enterprise Service Pack 1 - HOST
VirtualBox 5.1.14.r112924 Qt5.6.2 - GUEST

Situation is occurring only when I am running Virtual Box Guest (Ubuntu 16.04.2 LTS or other version), when Virtual Box is off everything is fine.

When I try to lock down the windows (Windows+L button) my windows is locking correctly. When I am trying to unlock windows by pressing CTRL+ALT+DELETE mouse work indicator start spinning, after 5 seconds it is stopping and I am unable to see login screen to provide windows password. It is just empty screen with the wallpaper and language button. The mouse is inactive, I can move it, but I cannot click anything (like this keyboard language button). My keyboard is active but when I press smth I am getting system sound (every button hit, bip bip bip...). After like two minutes, instead of getting login screen I am placed again in the screen to press CTRL+ALT+DELETE. This is endless loop hole. I just cannot login because of that. I need to reset computer.

I have tried using sticky keys (shift 5 times, it was enabled(popoup asking if I want to enable come out I clicked Yes)) instead of pressing CTRL+ALT+DELETE together but it is not helping at all.
I have checked guest Ubuntu shortcuts and I am sure I have nothing assigned to CTRL+ALT+DELETE (sticky keys would help is such way).

I just don't know how to solve it. Situation is repeated every time I am turning VirtualBox on and only then. Is there anybody with similar situation?

I addition I can say I have McAfee antivirus, and drive encryption manager. (that are my suspects, maybe they are not working fine in such combination). This is my corporate laptop so I cannot uninstall McAfee and check if it is working fine then.

[socratis]

Since your options are limited in what you can and can't try, let me ask you a couple of questions:

• Are you running your guest in full-screen or in seamless mode? If yes, don't.
• Have you checked the power options in the guest? If there is a screen saver/lock screen, disable it. If there is a power option to sleep/suspend/hibernate, disable them as well.

[harufu]

I am usually working in seamless mode, but I have tried also full screen mode and scaled mode. No matter what I am choosing the problem is still there. I have screen saver and lock disabled on guest. All options like hibernation are disabled.

[socratis]

The default mode is not full mode, it's not seamless mode, it's not scaled mode; it's windowed mode. Switch to windowed mode and follow a "start from cold-boot"/"observe error"/"shutdown" cycle. With the VM shut down completely (not paused or saved) or aborted, right-click on the VM in the VirtualBox Manager and select "Show Log". Save only the first "VBox.log", ZIP it and attach it to your response (see the "Upload attachment" tab below the reply form).