Keyboard shortcuts are a wonderful thing. They can save a great deal of time and allow a person to quickly navigate across documents, applications, and screens. I love keyboard shortcuts so much that I ditched the mouse in 2008 and haven't gone back¹! That said, people might experience some problems when trying to use keyboard shortcuts that involve the Ctrl key when running Windows in VirtualBox.
In my case, the problem was the result of a single checkbox in the Mouse Preferences.
When the "Show position of pointer when the Control key is pressed" checkbox is checked, the keystroke is not properly passed through to Windows. As a result, Ctrl+Z will result in a Z appearing on the screen rather than an undo action. Unchecking this option will resolve the problem, allowing us to properly copy, paste, cut, select all, undo, redo, print, and everything else we might want to accomplish with the Ctrl key. It's not a perfect solution, but it does work.
This does give me an idea, though. Perhaps I could make a quick little feature for Ubuntu that will grow the size of the mouse pointer when it's shaken a lot, similar to how it works on the current releases of OS X. It's a little gimmicky, but it does solve the problem of letting people know where the mouse is when working with large screens.