I've been using VirtualBox on a Windows 7 host for school for several weeks now. Suddenly today, my Ubuntu box locked up - I shut it down and rebooted, and now my screen isn't resizing as it should. Also, the "Auto Resize Guest-Display" option is greyed out.
I've tried reinstalling the guest additions, but this didn't solve anything. I have the display maximum resolution under Preferences->Display set to
I've tried the steps in this similar posting: http://www.blackmoreops.com/2014/01/18/fix-could-not-apply-stored-configuration-to-monitors-error-line-1-char-1-document-empty-contained-whitespace-error/
I'm a bit at a loss of what to try now. I can't work like this. The screen size is either very small, or super stretched.
Edit: What's even more strange is that I imported a backup of this VM that I had saved last night, and it's the same issue. I can all of a sudden not resize my VM window.