Undo works too often

I hate how in many applications "Undo" feature is so powerful, that I actually start to trust it. Today, I was using PowerPoint and hit "Ctrl+N" instead of "Ctrl+B". My presentation suddenly goes empty, and I instinctively hit "Ctrl+Z". Nothing happens and an hour of work flees down my spine... If you're going to make "Undo" not work for an action, make it a less scary one, not the "New..." command! :/