Although VirtualBox works very well in most cases, I have found that the way it handles the virtual keyboard and mouse inputs can cause serious problems. If I try to scroll a screen vertically, it's choppy approach to virtualizing the input causes a huge influx of scroll messages, and the whole PC locks up until the system is able to resolve all the accumulated messages, a process that can take hours. There is no way to get out of this situation besides pressing the power button until a shutdown dialog appears. But this means lost work because of a reboot.
The same choppy action effects a graphics game native to Windows, which is PinBall. If you try to play PinBall in virtual mode, you cannot launch a ball because it is the action of the space bar held down that draws the plunger back to shoot the ball. But instead of a continuous down state, the space bar is generating a long series of depressed messages, so the plunger quivers as it sees the space bar being repeatedly depressed and released in rapid succession.