I've finally found where the issue lies between the KeyCode plug-in and the native Keyboard plug-in. The Keyboard plug-in calls the preventDefault method at the end of the onKeyDown and onKeyUp functions. This basically short-circuits any other keyboard events which follow.
Ashley, is there any type of workaround that I can include in the KeyCode plug-in that will ignore the preventDefault call?
If not, I'm afraid the KeyCode plug-in is useless, when used in conjunction the Keyboard plug-in.