Originally Posted by SecretCode
What is your host key in Virtualbox? If it's winkey change it to something else. If it's something else (right ctrl is the default I think), pressing it will release input capture in your guest and allow the host to see all keystrokes.
I don't know of any reason why a vbox guest should capture keys - except for the host key - unless it already has the mouse input captured and/or the vbow window is focused.
I don't know the reason why, because my hostkey in vbox is RightCtrl. But still, despite capture or non-capture in vbox, Unity interrupts me and catches the WinKey.
I found out that it would be easier to change Mod4 in X11 of Gentoo or just change ModKey in awesome wm.