In XP, if you installed the Japanese code pages, you had that problem as well. Ctrl-B was an L-shaped character rather than a square, for example. And one of the characters (I think it was Ctrl-U) was just a blank "space".
Chances are that Vista installs this code page automatically. If you were to remove that code page if you don't need it, you may see the character again. I'm not sure if there's another way to see it without removing the code page(s) that are causing the issue.
